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<p xmlns:dct="http://purl.org/dc/terms/" xmlns:cc="http://creativecommons.org/ns#" class="license-text"><a rel="cc:attributionURL" property="dct:title" href="https://transfer.hft-stuttgart.de/gitlab/coors/neqmodplus-steinbeis/-/blob/master/ParameterCatalogsDocumentation">How to Implement Parameter Catalogs with Eclipse</a> by <span property="cc:attributionName">Kai-Holger Brassel</span>, Hamburg, is licensed under <a rel="license" href="https://creativecommons.org/licenses/by-nc-nd/4.0">CC BY-NC-ND 4.0<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/cc.svg?ref=chooser-v1" /><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/by.svg?ref=chooser-v1" /><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/nc.svg?ref=chooser-v1" /><img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;" src="https://mirrors.creativecommons.org/presskit/icons/nd.svg?ref=chooser-v1" /></a></p>
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= Parameter Catalogs for Simulation
Kai-Holger Brassel, Hamburg, <mail@khbrassel.de>
:toc:
:toclevels: 2
:compat-mode!:
This work by Kai-Holger Brassel, Hamburg, is licensed under https://creativecommons.org/licenses/by-nc-nd/4.0[CC BY-NC-ND 4.0]
image:https://mirrors.creativecommons.org/presskit/icons/cc.svg[cc,20]
image:https://mirrors.creativecommons.org/presskit/icons/by.svg[by,20]
image:https://mirrors.creativecommons.org/presskit/icons/nc.svg[nc,20]
image:https://mirrors.creativecommons.org/presskit/icons/nd.svg[nd,20]
Version: October 19^th^, 2020.
include::ParameterCatalogs1Overview.adoc[]
<<<
include::ParameterCatalogs2Creation.adoc[]
<<<
include::ParameterCatalogs3Usage.adoc[]
<<<
include::ParameterCatalogs4TychoBuild.adoc[]
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<body class="article">
<div id="header">
<h1>Parameter Catalogs for Simulation</h1>
<div class="details">
<span id="author" class="author">Kai-Holger Brassel, Hamburg, &lt;mail@khbrassel.de&gt;</span><br>
</div>
<div id="toc" class="toc">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#trueintroduction">Introduction</a>
<ul class="sectlevel2">
<li><a href="#truethe-bigger-picture">The Bigger Picture</a></li>
<li><a href="#truelessons-learned">Lessons Learned</a></li>
<li><a href="#truelow-code-development-of-parameter-catalogs">Low-Code-Development of Parameter Catalogs</a></li>
</ul>
</li>
<li><a href="#truehow-to-implement-parameter-catalogs-with-eclipse">How to Implement Parameter Catalogs with Eclipse</a>
<ul class="sectlevel2">
<li><a href="#trueeclipse-basics">Eclipse Basics</a></li>
<li><a href="#truesetup-eclipse-modeling-tools">Setup Eclipse Modeling Tools</a></li>
<li><a href="#truemodeling-parameter-catalogs-for-simulation-with-ecore">Modeling Parameter Catalogs for Simulation with Ecore</a></li>
<li><a href="#truegeneration-of-java-code-from-data-model">Generation of Java Code from Data Model</a></li>
<li><a href="#truegeneration-and-tweaking-of-user-interface">Generation and Tweaking of User Interface</a></li>
<li><a href="#truebonus-solutions-for-specific-modeling-problems">Bonus: Solutions for Specific Modeling Problems</a></li>
</ul>
</li>
<li><a href="#trueaccessing-and-using-parameter-catalogs">Accessing and Using Parameter Catalogs</a>
<ul class="sectlevel2">
<li><a href="#trueaccessing-xml-catalogs">Accessing XML-Catalogs</a></li>
<li><a href="#truecreate-insel-models-with-handlebars-templates">Create Insel Models with Handlebars Templates</a></li>
</ul>
</li>
<li><a href="#truebuild-parameter-catalog-applications-with-eclipse-tycho">Build (Parameter Catalog) Applications with Eclipse Tycho</a>
<ul class="sectlevel2">
<li><a href="#truecreate-an-eclipse-application">Create an Eclipse Application</a></li>
<li><a href="#trueuse-maven-and-tycho-as-build-system">Use Maven and Tycho as Build System</a></li>
<li><a href="#truedeploy-to-p2-repository">Deploy to P2 Repository</a></li>
<li><a href="#trueversioning-and-collaboration">Versioning and Collaboration</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p>This work by Kai-Holger Brassel, Hamburg, is licensed under <a href="https://creativecommons.org/licenses/by-nc-nd/4.0"">CC BY-NC-ND 4.0</a>
<span class="image"><img src="https://mirrors.creativecommons.org/presskit/icons/cc.svg" alt="cc" width="20"></span>
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<span class="image"><img src="https://mirrors.creativecommons.org/presskit/icons/nd.svg" alt="nd" width="20"></span></p>
</div>
<div class="paragraph">
<p>Version: October 19<sup>th</sup>, 2020.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="trueintroduction"><a class="anchor" href="#trueintroduction"></a>Introduction</h2>
<div class="sectionbody">
<div class="admonitionblock important">
<table>
<tr>
<td class="icon">
<i class="fa icon-important" title="Important"></i>
</td>
<td class="content">
<div class="paragraph">
<p>This introduction talks about the work of the author and others, but without bibliographic references. Currently, it is just meant as background to better understand the technical documentation in the sections to follow.
Maybe it could be developed into a more serious paper later.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The overall motivation for the work on parameter catalogs for simulation is to make easier to develop and perform computer simulations in complex and <em>data rich</em> domains like building physics, transportation, and all kinds of urban infrastructure.</p>
</div>
<div class="sect2">
<h3 id="truethe-bigger-picture"><a class="anchor" href="#truethe-bigger-picture"></a>The Bigger Picture</h3>
<div class="paragraph">
<p>A good part of computer science was and is driven by the motivation to make it easier to develop computer programs of all sorts.
"Higher" programming languages were invented to make programs human readable and soon special constructs for <em>functional programming</em> (computation without side effects) and <em>structured programming</em> (computation without go to statements) were introduced to help programmers writing and understanding ever growing programs.
Then, between 1962 and 1967, program language Simula was developed especially to deal with the challenges of simulating systems comprising of many different types of objects.
This opened the door to more direct computer representations of real world objects, their attributes, relationships and behavior, ultimately leading to <em>object-oriented</em> software development that today is embodied in programming languages like Java, C++, Python, and graphical notations like the Unified Modeling Language (UML).</p>
</div>
<div class="paragraph">
<p>While these achievements had boosted the productivity of software developers, still the creation of correct, efficient and maintainable programs&#8201;&#8212;&#8201;including simulations&#8201;&#8212;&#8201;required a big deal of expert knowledge and experience.
To overcome this bottleneck, starting in the 70s, so called 4th generation languages entered the stage.
These languages were tailored to specific tasks like statistics ("S" 1976, "R" being its successor), database programming (SQL 1979), or simulation (MATLAB around 1979, Mathematica 1988, Modellica 1999) to name a few.
By sacrificing generality, these special languages become more accessible to domain experts, not just trained software developers.
To flatten the learning curve even more, formal <em>graphical</em> languages for special purposes were invented, e.g. Simulink for block diagram simulation models in 1984, Entity-Relationship-Diagrams for data modeling in 1976, UML for object-oriented systems design in the 1990s, or graphical languages to specify business and also scientific workflows around 2000.</p>
</div>
<div class="paragraph">
<p>This very short history of technologies for development of software in general, and simulations in particular, shall illuminate the tools at our disposal:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>general purpose programming languages that combine structured, functional and object-oriented approaches to enable the creation of big, modular software systems, often called "programming in the large"</p>
</li>
<li>
<p>formal textual domain specific languages (DSLs) dedicated to solve specific tasks with ease</p>
</li>
<li>
<p>formal graphical DSLs.</p>
</li>
</ul>
</div>
<div class="exampleblock">
<div class="content">
<div class="paragraph">
<p>Note that DSLs more tend to describe <em>what</em> shall be achieved by a computation instead of describing in detail, <em>how</em> to achieve it.
Therefore, DSLs usually look more like a model than like an algorithm.</p>
</div>
</div>
</div>
<div class="paragraph">
<p>Now back to the task at hand.</p>
</div>
<div class="paragraph">
<p>Some domains deal with a few types of simple objects to be simulated.
Take the building blocks of an electric circuit as an example.
The algorithms to simulate these correctly and efficiently may be quite complex&#8201;&#8212;&#8201;the model elements usually can be described by very few parameters like resistance or capacity.
More complex domains like (regenerative) energy systems or building physics deal with more complex objects to be simulated, e.g. PV modules or layered walls of buildings, often coming in different types and configurations, and dozens of possibly interdependent parameters.</p>
</div>
</div>
<div class="sect2">
<h3 id="truelessons-learned"><a class="anchor" href="#truelessons-learned"></a>Lessons Learned</h3>
<div class="paragraph">
<p>First a note on terminology: Instead of <em>parameter catalogs</em> in SimStadt we used term <em>library</em> like in <em>building physics library</em>. Obviously this was not a good choice, since <em>library</em> is used a lot in IT and programming with all sorts of meaning. Instead we started to talk about <em>data catalogs</em>, but in data science this term has specific meaning, namely: catalogs of data and data sources.
Since our catalogs, first of all, shall grant structured access to parameters for simulated entities <em>parameter catalog</em> sounds more appropriate to me.</p>
</div>
<div class="paragraph">
<p>The problem of navigating huge parameter spaces and assembling complex simulation models popped up as the author worked on a diagram editor for <strong>INSEL</strong>, a simulation language and runtime environment developed for renewable energy systems simulation.
To make existing catalogs on weather data, solar panels and inverter modules accessible to the modeler, special dialogs were added to the INSEL user interface that allowed browsing through the catalogs.
Using this browsers, the modeler would choose a weather station, panel or inverter to parameterize a corresponding INSEL function-block.
However, there are some severe disadvantages with this approach:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Parameter catalogs were stored in a proprietary data format on disk within the INSEL application distribution, meaning they could not used independently from INSEL by other interested parties (systems or users).</p>
</li>
<li>
<p>The catalogs have to be maintained by editing text files manually.</p>
</li>
<li>
<p>While INSEL modeler could browse the catalogs, searching and sorting were not supported.</p>
</li>
<li>
<p>Development of Java Swing UIs for the different kind of catalogs is time consuming as is their maintenance, e.g. if a catalog data format were to change.</p>
</li>
<li>
<p>Putting UIs to handle big amounts of data into a diagram editor is not very user friendly.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>From 2013 to 2016, the simulation platform <strong>SimStadt</strong> was developed to make specific modeling and simulation workflows accessible to experts in urban planning and energy systems.
Using INSEL and other simulators under the hood, the usage of 3D city data, provided as CityGML files, was a core requirement of this project.</p>
</div>
<div class="paragraph">
<p>To enable simulation of, say, the heating demand of a district, geometric building data had to be enriched with data on building physics and usage.
To do so, existing informations about building physics and usage&#8201;&#8212;&#8201;often only available as informal typologies or tables&#8201;&#8212;&#8201;had to be provided to the SimStadt user on an abstract level, e.g. to choose between refurbishment scenarios.
At the same time, specific building configurations and parameter sets had to be injected into the simulation models to obtain the desired results.</p>
</div>
<div class="paragraph">
<p>Again, we implemented parameter catalogs to fulfill these requirements, but compared to the quite simple catalogs used in INSEL, the data for building materials, window, wall and roof types as well as the typologies of buildings, households, usage patterns, and so on were more intricate.
They had to be created iteratively in collaboration with domain experts.
In this situation, manual coding data formats and access with a general programming language would have led to relatively long iteration cycles and high communication effort between programmer and domain expert.
Instead, we decided to use a DSL for data modeling and use code generation whenever possible.
Since SimStadt was developed within the Java eco-system we followed this standard approach:<sup class="footnote">[<a id="_footnoteref_1" class="footnote" href="#_footnotedef_1" title="View footnote.">1</a>]</sup></p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Developer and domain expert create a first version of the data model as XML Schema Definition (our DSL).</p>
</li>
<li>
<p>For plausibility checks one would use any standard XML editor to create example data conforming to the XSD.</p>
</li>
<li>
<p>With JAXB (Java Architecture for XML Binding) Java code is generated to read our XML catalogs into Java objects that, in turn, can be accessed by SimStadt workflows to generate and parameterize simulations.</p>
</li>
<li>
<p>If required, developer and domain expert go back to step one to refine data model and catalog data.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>After the data model for building physics catalogs had matured, we developed a desktop application for convenient creation and maintenance of building physics data catalogs separate from SimStadt.
It was developed in Java with a user interface written in JavaFX and was well received by domain experts.</p>
</div>
<div class="paragraph">
<p>However, as a different catalog&#8201;&#8212;&#8201;this time for building usages&#8201;&#8212;&#8201;had to be created, it was quite difficult to reuse the XML schema and application code from the building physics catalog: The usage catalog data model was "pressed" into a form similar to the building physics catalog data model, and the UI code was "over-engineered" to accommodate both catalog&#8217;s requirements.</p>
</div>
</div>
<div class="sect2">
<h3 id="truelow-code-development-of-parameter-catalogs"><a class="anchor" href="#truelow-code-development-of-parameter-catalogs"></a>Low-Code-Development of Parameter Catalogs</h3>
<div class="paragraph">
<p>From INSEL and SimStadt we learned, that manual and automatic construction and parameterization of complex simulation models with many types of interrelated objects should be supported be the means of domain specific parameter catalogs.</p>
</div>
<div class="paragraph">
<p>Close collaboration with domain experts in designing and implementing these catalogs in short development cycles is desirable.</p>
</div>
<div class="paragraph">
<p>Parameter catalogs and the software for their creation, maintenance and deployment should be independent of any specific simulation software, (a) to be reusable and (b) not to overload simulation applications.</p>
</div>
<div class="paragraph">
<p>In SimStadt, catalog development was partly facilitated by a textual DSL for data modeling (XML schema language) and automatic generation of Java code from it.
On the other hand, user interfaces and generation and parameterization of simulations from templates within SimStadt workflows had still to be coded manually hindering the routinely creation of new catalogs.</p>
</div>
<div class="paragraph">
<p>Now, in 2020, several developments in different projects provide an opportunity to re-think the topic of parameter catalogs for simulations, namely:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Plans for a new Urban Simulation Platform at Concordia University, Montreal.</p>
</li>
<li>
<p>New implementation of INSEL user interface based on the Eclipse application framework and Eclipse-Sirius diagram editors.</p>
</li>
<li>
<p>Enhancement of existing building physics and usage catalogs from SimStadt and their adaptation to new regions.</p>
</li>
<li>
<p>Development of a new comprehensive catalog of electric systems components to be used in SimStadt as well as in Concordia&#8217;s Urban Simulation Platform.</p>
</li>
</ol>
</div>
<div class="exampleblock">
<div class="content">
<div class="paragraph">
<p>In what follows, the new technology stack used to implement (4) is documented in detail.
It uses four technologies to replace manual coding by code generation from models:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><em>Ecore</em> to model the catalog&#8217;s data and generate Java classes and persistence layer from it.</p>
</li>
<li>
<p><em>EMF Forms</em> for modeling and generating tables, forms and buttons to <strong>c</strong>reate, <strong>r</strong>ead, <strong>u</strong>pdate, and <strong>d</strong>elete data (CRUD).</p>
</li>
<li>
<p><em>E4</em>, the Eclipse way of modeling the application user interface itself, e.g. the placement and behavior of views, editors, toolbars, menus, and more.</p>
</li>
<li>
<p>A template engine called <em>Handlebars</em> to generate fully parameterized simulation models from textual templates without programming.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>The new technology stack is rooted in the Eclipse application framework and eco-system.<sup class="footnote">[<a id="_footnoteref_2" class="footnote" href="#_footnotedef_2" title="View footnote.">2</a>]</sup>
Its main advantage is the possibility to implement CRUD applications like parameter catalogs and their underlying data models with no or very view lines of handwritten code (<em>low-code-development</em>).</p>
</div>
</div>
</div>
<div class="paragraph">
<p>Plans are to use the same approach also for implementation of (3).
Since task (2) and maybe (1) will use Eclipse, too, close integration of parameter catalogs and simulation environments seems feasible.
E.g., a user could drag an electric system component from a catalog onto an INSEL block for parametrization.</p>
</div>
<div class="paragraph">
<p>The Eclipse application framework offers:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>OSGI plug-in mechanism and UI framework for integrating applications and services</p>
</li>
<li>
<p><em>E4</em> application model to declaratively describe user interface&#8217;s structure</p>
</li>
<li>
<p>General notion of <em>project</em> with specific file types, help system, preferences etc.</p>
</li>
<li>
<p>IDE support for important general purpose languages like Java, <a href="https://marketplace.eclipse.org/content/pydev-python-ide-eclipse">Python</a>, Ruby, C, Fortran, C++</p>
</li>
<li>
<p>Support for creating textual and graphical DSLs (<a href="https://www.eclipse.org/Xtext">XText</a>, <a href="https://www.eclipse.org/sirius">Sirius</a>)</p>
</li>
<li>
<p>Industry proven DSLs and code generators for data models and form based UIs via the <a href="https://www.eclipse.org/modeling/emf"><em>Eclipse Modeling Framework</em></a> (EMF) providing:</p>
<div class="ulist">
<ul>
<li>
<p><a href="https://www.eclipse.org/ecoretools"><em>Ecore</em></a> for model driven generation of Java classes and persistence layers for XML or data bases</p>
</li>
<li>
<p><a href="https://eclipsesource.com/blogs/tutorials/emf-forms-view-model-elements"><em>EMF Forms</em></a> for describing and generating form based UIs</p>
</li>
<li>
<p>Mechanisms to adapt or extend data models and forms to special needs (e.g., we added quantities&#8201;&#8212;&#8201;that is numbers <em>with units</em>&#8201;&#8212;&#8201;to Ecore and EMF Forms, a feature very important for parameter catalogs)</p>
</li>
</ul>
</div>
</li>
<li>
<p>Rich open source eco-system with lots of plugins and projects important for an urban simulation platform:</p>
<div class="ulist">
<ul>
<li>
<p>model server for distributed access and work on Ecore models, including model comparison and migration (<a href="https://projects.eclipse.org/projects/modeling.emf.cdo">CDO</a>, <a href="https://www.eclipse.org/emf/compare">EMFCompare</a>)</p>
</li>
<li>
<p>a <a href="https://pyecore.readthedocs.io/en/latest">Python implementation of Ecore</a></p>
</li>
<li>
<p>GIS: storage, processing, and visualization of geographical data (list of projects under the umbrella <a href="https://projects.eclipse.org/projects/locationtech">LocationTech</a>, e.g. user-friendly desktop internet GIS <a href="http://udig.refractions.net">uDig</a>)</p>
</li>
<li>
<p>workbench for traffic simulation (<a href="https://www.eclipse.org/sumo">SUMO</a>)</p>
</li>
<li>
<p>spatial multi-agent-simulation (<a href="https://gama-platform.github.io/wiki/Home">GAMA-Platform</a>)</p>
</li>
<li>
<p>scientific workflows (<a href="https://projects.eclipse.org/projects/science.triquetrum">Triquetrum</a>)</p>
</li>
<li>
<p>visualizations (<a href="https://www.eclipse.org/nebula/widgets/visualization/visualization.php">Nebula</a>)</p>
</li>
<li>
<p>machine learning (<a href="https://deeplearning4j.org">deeplearning4j</a>)</p>
</li>
<li>
<p>45+ projects in the area of <a href="https://iot.eclipse.org">IoT</a></p>
</li>
<li>
<p>&#8230;&#8203;</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<div class="paragraph">
<p>As always, all that glitters is not gold. When we go through the details below, some bugs and inconsistencies, typical for open source projects of this age and size, have to be addressed.</p>
</div>
<div style="page-break-after: always;"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="truehow-to-implement-parameter-catalogs-with-eclipse"><a class="anchor" href="#truehow-to-implement-parameter-catalogs-with-eclipse"></a>How to Implement Parameter Catalogs with Eclipse</h2>
<div class="sectionbody">
<div class="paragraph">
<p>To build a new parameter catalog from scratch, we first have to understand some basics about Eclipse, and then install the correct Eclipse package.
Thereafter, we can model our data with Ecore considering some best practices, followed by the generation of Java classes and user interface (UI).
We, then, will add some plug-ins to "pimp" our Eclipse installation, (a) to enable deployment of parameter catalog applications, and (b) to add units and quantities to the mix.
Some hints on special modeling problems and versioning parameter catalogs conclude this how-to guide.</p>
</div>
<div class="sect2">
<h3 id="trueeclipse-basics"><a class="anchor" href="#trueeclipse-basics"></a>Eclipse Basics</h3>
<div class="paragraph">
<p><a href="https://en.wikipedia.org/wiki/Eclipse_(software)">Eclipse</a> was originally developed by IBM and became Open Source in 2001.
It is best known for its Integrated Development Environments (<em>Eclipse IDEs</em>), not only for Java, but also for C++, Python and many other programming languages.
These IDEs are created on top of the Eclipse Rich Client Platform (Eclipse RCP), an application framework and plug-in system based on Java and OSGi.
Eclipse RCP is foundation of a plethora of general-purpose applications, too.</p>
</div>
<div class="paragraph">
<p>First time users of Eclipse better understand the following concepts.</p>
</div>
<div class="paragraph">
<div class="title">Eclipse Packages</div>
<p>An Eclipse package is an Eclipse distribution dedicated to a specific type of task.<sup class="footnote">[<a id="_footnoteref_3" class="footnote" href="#_footnotedef_3" title="View footnote.">3</a>]</sup>
A list of packages is available at <a href="https://www.eclipse.org/downloads/packages/">eclipse.org</a>.
Beside others it contains <em>Eclipse IDE for Java Developers</em>, <em>Eclipse IDE for Scientific Computing</em>, and the package we will use: <em>Eclipse Modeling Tools</em>.
Note that third parties offer many other packages, e.g. <em>GAMA</em> for multi-agent-simulation or <em>Obeo Designer Community</em> for creating Sirius diagram editors.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="paragraph">
<p>Several Eclipse packages can be installed side by side, even different releases of the same package. Multiple Eclipse installations can run at the same time, each on its own <em>workspace</em> (see below).</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<div class="title">Plug-ins / Features</div>
<p>An installed Eclipse package consists of a runtime core and a bunch of additional plug-ins.
Technically, a plug-in is just a special kind of Java archive (JAR file) that uses and can be used by other plug-ins with regard to OSGi specifications.
Groups of plug-ins that belong together are called a <em>feature</em>.</p>
</div>
<div class="paragraph">
<p>Often, a user will add plug-ins or features to an Eclipse installation to add new capabilities.
E.g. writing this documentation within my Eclipse IDE is facilitated by the plug-in <a href="https://marketplace.eclipse.org/content/asciidoctor-editor">Asciidoctor Editor</a>.
Plug-ins can easily be installed via main menu command <code>Help → Eclipse Marketplace&#8230;&#8203;</code> or <code>Help → Install New Software&#8230;&#8203;</code>.
Some plug-ins may be self-made like our plug-in <code>de.hftstuttgart.units</code> that enables Ecore to deal with quantities.
These may be provided via <em>Git</em> or as download and have to be added to an Eclipse installation manually.</p>
</div>
<div class="paragraph">
<div class="title">Git</div>
<p><a href="https://git-scm.com">Git</a> is the industry standard for collaborative work on, and versioning of, source code and other textual data.
Collaborative development of parameter catalogs benefits massively from using Git.
Git support is built into <em>Eclipse Modeling Tools</em>, the Eclipse package we will use.
However, if Eclipse needs to connect to a Git server that uses SSH protocol (not HTTPS with credentials), access configuration is more involved and may be dependent on your operating system.</p>
</div>
<div class="paragraph">
<p>Some users, anyway, prefer to use Git from the command line or with one of the client application listed <a href="https://git-scm.com/downloads/guis">here</a>, e.g. <a href="https://tortoisegit.org">TortoiseGit</a> for Windows.</p>
</div>
<div class="paragraph">
<p>While it is required to get Git working at some point, we won&#8217;t refer to it in this document and, for now, do not cover the installation of Git on your machine or configuration of Git in Eclipse.</p>
</div>
<div class="paragraph">
<div class="title">Workspaces</div>
<p>When you start a new Eclipse installation for the first time, you are asked to designate a new directory in your file system to store an <em>Eclipse workspace</em>.
Eclipse is always running with exact one workspace open.
As the name implies, a workspace stores everything needed in a given context of work, namely a set of related projects the user is working on as well as meta-data like preference settings, the current status of projects, to do lists, and more.
In case a user wants to work in different contexts, e.g. on different tasks, command <code>File &#8594; Switch Workspace</code> allows to create additional workspaces and to switch between them.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="paragraph">
<p>Any plug-in from the original Eclipse package or installed by the user later will be copied into the Eclipse installation directory, <strong>not</strong> in any workspace.
Configuration and current state of plug-ins, on the other hand, are stored in workspaces.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<div class="title">Projects</div>
<p>An Eclipse project is a technical term for a directory that often contains:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>files of specific types for source code, scripts, XML files or other data</p>
</li>
<li>
<p>build settings, configurations</p>
</li>
<li>
<p>dependency definitions (remember the dependencies between plug-ins above?)</p>
</li>
<li>
<p>other Eclipse projects.</p>
</li>
</ul>
</div>
<div class="paragraph">
<p><code>File &#8594; New &#8594; Project&#8230;&#8203;</code> offers many different types of projects that the user can choose from, e.g. Java projects to create Java programs, Ecore modeling projects, or general projects, that simple hold some arbitrary files.<sup class="footnote">[<a id="_footnoteref_4" class="footnote" href="#_footnotedef_4" title="View footnote.">4</a>]</sup></p>
</div>
<div class="admonitionblock warning">
<table>
<tr>
<td class="icon">
<i class="fa icon-warning" title="Warning"></i>
</td>
<td class="content">
<div class="paragraph">
<p>Files that do not belong to a project are invisible for Eclipse!</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The projects belonging to a workspace can either be directly stored within the workspace as sub-directories (the default offered to the user when creating a new project), or linked from it, that is the workspace just holds a link to the project directory that lives somewhere in the file system outside of the workspace.
Linking allows to work with the same projects in different workspaces.</p>
</div>
<div class="paragraph">
<p>While it sometimes makes sense to share or exchange workspaces between users,<sup class="footnote">[<a id="_footnoteref_5" class="footnote" href="#_footnotedef_5" title="View footnote.">5</a>]</sup>, I do not recommend this for now.
Projects, in contrast, are shared between users most of the time, usually via Git.
In general, I would suggest to store Eclipse projects outside workspaces at dedicated locations in the user&#8217;s file system.
That way, we can follow the convention that local Git repositories should all be located under
<code>&lt;userhome&gt;/git</code>.</p>
</div>
</div>
<div class="sect2">
<h3 id="truesetup-eclipse-modeling-tools"><a class="anchor" href="#truesetup-eclipse-modeling-tools"></a>Setup Eclipse Modeling Tools</h3>
<div class="paragraph">
<div class="title">Install Java</div>
<p>Eclipse runs on 64-bit versions of Windows, Linux, and macOS and requires an according Java Development Kit (JDK), version 11 or higher, to be installed on your machine.
Even if such JDK already exists, please download OpenJDK, version <strong>15</strong> or newer for your operating system from <a href="https://adoptopenjdk.net">AdoptOpenJDK</a>.
<sup class="footnote">[<a id="_footnoteref_6" class="footnote" href="#_footnotedef_6" title="View footnote.">6</a>]</sup>
Choose <code>HotSpot</code> as Java Virtual Machine.
Installation process is straight forward, but you can also find links to exhaustive instructions for your operating system.</p>
</div>
<div class="paragraph">
<p>New Java versions appear every six months, so one could tend to stick with older version 11 that comes with long time support (LTE) until version 17 arrives in autumn 2021.
However, actual version 15 conforms to the latest security measures built into macOS Catalina, so it is a must if software we build here shall be deployed to these systems, too.</p>
</div>
<div class="paragraph">
<p>Note that different versions of Java coexist peacefully.</p>
</div>
<div class="paragraph">
<div class="title">Install Eclipse Modeling Tools</div>
<p>Now its time to download and install the correct Eclipse package <em>Eclipse Modeling Tools</em>, version 2020-09 or newer.<sup class="footnote">[<a id="_footnoteref_7" class="footnote" href="#_footnotedef_7" title="View footnote.">7</a>]</sup>
Please go to <a href="https://www.eclipse.org/downloads/packages">Eclipse download page for packages</a>.
On this page you may see <em>"Try the Eclipse Installer"</em> or similar.
Do <strong>not</strong> follow this advice, since we want more control over what versions of Java and Eclipse shall be installed.
Instead, look for package <em>Eclipse Modeling Tools</em> and follow the link for your operating system on the right:</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/EclipseDownload.gif" alt="EclipseDownload">
</div>
<div class="title">Figure 1. Download links for Eclipse Modeling Tools package</div>
</div>
<div class="paragraph">
<p>Finally, you can click on <code>Download</code> and wait for the 400 something MB package to arrive.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="paragraph">
<p>Depending on the operating system, several security dialogs have to be acknowledged during installation and first launch of Eclipse.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>The downloaded installation file contains the application simply named <code>Eclipse</code> ready to be copied into <code>Applications</code> on macOS or be installed in <code>Programs</code> on Windows.
Since later you may add other Eclipse packages&#8201;&#8212;&#8201;or different versions of the same package&#8201;&#8212;&#8201;I suggest to rename the application more significantly to <code>EclipseModeling2009</code> or similar.</p>
</div>
<div class="paragraph">
<p>After installation has finished launch Eclipse for the first time and you will see a dialog for choosing a new empty directory as its workspace.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/SelectWorkspaceDirectory.gif" alt="SelectWorkspaceDirectory" width="500">
</div>
<div class="title">Figure 2. Initial Dialog to Choose a Workspace Directory</div>
</div>
<div class="paragraph">
<p>Again, more workspaces might come into existence later, so replace the proposed generic directory path and name with a more specific one, e.g.<code>EclipseModelingWS</code>.
The Eclipse main window appears with a Welcome Screen open.
It contains links to exhaustive documentation on concept, features and usage of Eclipse that might be of interest later, especially:</p>
</div>
<div class="ulist">
<ul>
<li>
<p>Overview</p>
<div class="ulist">
<ul>
<li>
<p>Workbench basics</p>
<div class="ulist">
<ul>
<li>
<p>Concepts: features, resources, perspectives, views, editors</p>
</li>
<li>
<p>Opening perspectives and views</p>
</li>
<li>
<p>Installing new software manually</p>
</li>
</ul>
</div>
</li>
<li>
<p>Team support with Git</p>
</li>
</ul>
</div>
</li>
<li>
<p>Learn how to use the Ecore diagram editor</p>
</li>
<li>
<p>Launch the Eclipse Marketplace</p>
</li>
</ul>
</div>
<div class="paragraph">
<p>For now, you can dismiss the welcome screen. It can be opened anytime by executing <code>Help &#8594; Welcome</code></p>
</div>
</div>
<div class="sect2">
<h3 id="truemodeling-parameter-catalogs-for-simulation-with-ecore"><a class="anchor" href="#truemodeling-parameter-catalogs-for-simulation-with-ecore"></a>Modeling Parameter Catalogs for Simulation with Ecore</h3>
<div class="paragraph">
<p>Now you should see the initial layout of Eclipse with <em>Model Explorer</em> and <em>Outline</em> on the left and a big empty editing area with <em>Properties</em> view below to the right.</p>
</div>
<div class="paragraph">
<p>Since we will use Ecore diagrams for data modeling, create your first Ecore modeling project now:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Execute <code>File &#8594; New &#8594; Ecore Modeling Project</code> from main menu&#8201;&#8212;&#8201;not <code>Modeling Project</code>!</p>
</li>
<li>
<p>Name it <code>demo.catalog</code> and click <code>Next &gt;</code></p>
</li>
<li>
<p>Uncheck <code>Use Default Location</code> so that the new project is <strong>not</strong> stored in workspace, but a different directory you create/choose, then click <code>Next &gt;</code></p>
</li>
<li>
<p>Provide <code>democatalog</code> as main Java package name and click <code>Finish</code>.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>Eclipse should look like below with an new empty graphical Ecore diagram editor opened.
The diagram is automatically named <code>democatalog</code> after the package name for the Java classes that will be generated from it (provided above).
The <em>Model Explorer</em> shows the contents of the new Ecore modeling project.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/DemoCatalogEmpty.png" alt="DemoCatalogEmpty">
</div>
<div class="title">Figure 3. New Ecore Modeling Project</div>
</div>
<div class="paragraph">
<p>To get your feet wet, do this:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Drag a <em>Class</em> from the palette on the right onto the editor&#8217;s canvas: it will materialize as a rectangle labeled <code>NewEClass1</code>.</p>
</li>
<li>
<p>The class symbol should be selected initially, so you can see its attributes in the <em>Properties</em> view.</p>
</li>
<li>
<p>In there replace <code>NewEClass1</code> by <code>EnergyComponentsCatalog</code> to rename the class.</p>
</li>
<li>
<p>Click anywhere on the canvas and notice that the class symbol is deselected and the toolbar at the top adapts accordingly.</p>
</li>
<li>
<p>In the toolbar change <code>100%</code> to <code>75%</code> to scale diagram.</p>
</li>
<li>
<p>Execute <code>File &#8594; Save</code> to save model and diagram on disk.</p>
</li>
<li>
<p>Close diagram editor <code>democatalog</code> by closing its tab.</p>
</li>
<li>
<p>Reopen saved diagram by double click on entry <code>democatalog</code> in <em>Model Explorer</em>.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>Technically, everything is in place now to begin modeling the data that the projected catalog shall contain.
Except &#8230;&#8203; understanding the basics of object-oriented modeling would be helpful.
This is why developers should support domain experts at this stage.</p>
</div>
<div class="paragraph">
<div class="title">Model Data with Class Diagrams</div>
<p>Ecore diagrams are simplified UML class diagrams.
Here some resources on what this is all about:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><a href="http://www.cs.toronto.edu/~sme/CSC340F/slides/11-objects.pdf">Toronto Lecture on Object Oriented Modeling</a></p>
</li>
<li>
<p><a href="http://agilemodeling.com/artifacts/classDiagram.htm">UML 2 Class Diagrams: An Agile Introduction</a></p>
</li>
<li>
<p><a href="https://www.amazon.de/UML-Classroom-Einführung-objektorientierte-Modellierung-ebook/dp/B00AIBE1QA/ref=sr_1_2?__mk_de_DE=ÅMÅŽÕÑ&amp;dchild=1&amp;keywords=UML&amp;qid=1585854599&amp;sr=8-2">UML @ Classroom: Eine Einführung in die objektorientierte Modellierung (German Book)</a></p>
</li>
</ul>
</div>
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<div class="paragraph">
<p>Beginners are strongly encouraged to read the first two resources.
The first one contains a gentle introduction, especially suited for domain experts.
The second one can also serve as reference.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>We will touch central object-oriented concepts <em>Class</em>, <em>Object</em>, <em>Attribute</em>, <em>Association</em>, <em>Composition</em>, and <em>Multiplicity</em> in an example below, but work through above sources to get a deeper understanding and to enhance your modeling skills.</p>
</div>
<div class="paragraph">
<p>Note that above sources differentiate between <em>conceptual</em> and <em>detailed</em> models.
All in all we go for detailed models, since only these contain enough information to generate code.
Having said this, it is usually a good idea to have two or three conceptual iterations at a white board to agree on the broad approach before going too much into detail.
But even if one starts with Ecore models right away, these also can be adapted any time to follow a new train of thought.</p>
</div>
<div class="paragraph">
<p>See here the essential and typical structure of a parameter catalog in a class diagram.
Instead of artificial example classes like <em>Foo</em> and <em>Bar</em> it shows classes from an existing catalog, albeit in very condensed form.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="http://localhost:56397/afx/cache/8068a4d732d1847a062d97696687b38f.png" alt="8068a4d732d1847a062d97696687b38f">
</div>
<div class="title">Figure 4. Principle Structure of a Parameter Catalog</div>
</div>
<div class="paragraph">
<p>The diagram models four types of technical components whose data shall be stored in the catalog, e.g. for parameterization of simulation models later: <em>Boiler</em>, <em>CombinedHeatPower</em>, <em>SolarPanel</em>, and <em>Inverter</em>.</p>
</div>
<div class="paragraph">
<p>The catalog itself is represented by class <em>EnergyComponentsCatalog</em>.
Unlike dozens, hundreds, or even thousands of objects to be cataloged&#8201;&#8212;&#8201;Boilers, Inverters etc.&#8201;&#8212;&#8201;there will be just exactly <strong>one</strong> catalog object in the data representing the catalog itself.
Its "singularity" is not visible in the class diagram, but an <em>Ecore</em> convention requires that all objects must form a composition hierarchy with only one root object.</p>
</div>
<div class="paragraph">
<div class="title">Composition</div>
<p>If, in the domain, one object is composed of others, this is expressed by a special kind of association called <em>composition</em>.
Compositions are depicted as a link with a diamond shape attached to the containing object. In the <em>Boiler</em> case said link translates to: The <em>EnergyComponentsCatalog</em> contains&#8201;&#8212;&#8201;or is composed of&#8201;&#8212;&#8201;zero or more (<code>0..*</code>) boiler objects stored in a list named <code>boilers</code>.</p>
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<p>Note that class names&#8201;&#8212;&#8201;despite the fact that they model a set of similar objects&#8201;&#8212;&#8201;are always written in <em>singular</em>! They are written in <a href="https://en.wikipedia.org/wiki/Camel_case">Camel case notation</a> starting with an upper case letter. Associations and attributes are written the same way, but starting with a lower case letter. Names for list-like associations and attributes usually are written in plural form.</p>
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</td>
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</div>
<div class="paragraph">
<div class="title">Inheritance</div>
<p>Besides composition of <strong>objects</strong>, the model above shows another, completely different, kind of hierarchy: the inheritance hierarchy between <strong>classes</strong>.
Whenever classes of objects share the same attributes or associations, we don&#8217;t like to repeat ourselves by adding that attribute or relation to all classes again and again.
Instead, we add a <em>super class</em> to define common attributes and associations and connect it to <em>sub classes</em> that will automatically <em>inherit</em> all the features of their super class.</p>
</div>
<div class="paragraph">
<p>In our example above, common to all four energy components are attributes <code>modelName</code> and <code>revisionYear</code>, thus these are modeled by class <code>EnergyComponent</code> that is directly or indirectly a super class of <em>Boiler</em>, <em>CombinedHeatPower</em>, <em>SolarPanel</em>, and <em>Inverter</em>.
Similar, <em>Boiler</em> and <em>CombinedHeatPower</em> share attribute <code>installedThermalPower</code> factored out by class <em>ChemicalEnergyDevice</em>.</p>
</div>
<div class="paragraph">
<div class="title">Associations</div>
<p>You probably noticed a fifth type of objects contained in the catalog, namely <code>Manufacturer</code> objects stored in list <code>manufactureres</code>.
How come? Ok, here is the story:</p>
</div>
<div class="sidebarblock">
<div class="content">
<div class="title">Domain Expert Meets Developer</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;I&#8217;d like to store a component&#8217;s manufacturer. Shall I add a String attribute <code>manufacturerName</code> to all classes like <em>Boiler</em>, <em>Inverter</em> and so on to store the manufacturer&#8217;s name?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em> shudders: &#8220;Well, what do you mean by "&#8230;&#8203; and so on"?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;Basically, I mean all energy components.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Fine. We already have a class representing all those energy components, brilliantly named <em>EnergyComponent</em>. Thus, we can define <code>manfacturerName</code> there, following one of Developer&#8217;s holy principles: "<em>DRY</em>&#8201;&#8212;&#8201;Don&#8217;t repeat yourself!"
By the way: Is the name all you want to know about manufacturers?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;Mhm, maybe we need to know if they are still in business &#8230;&#8203;&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;&#8230;&#8203; or even since when they were out of business, if at all &#8230;&#8203;&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;&#8230;&#8203; and the country or region they are active.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Ok, so it&#8217;s not just the name&#8201;&#8212;&#8201;we need a class <code>Manufacturer</code> to model all these information.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em> sighs.</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Come on, its not that hard to add a class to our data model, isn&#8217;t it?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;Ok, but how can we express what components a manufacturer produces?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Wasn&#8217;t it the other way around? I thought, you just wanted to know the manufacturer of a component?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;What is the difference?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;In data modeling, it is the difference between a uni-directional and a bi-directional association.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;&#8230;&#8203;?&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Let&#8217;s put it that way: The difference between a link with an arrow on one side or on both sides.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;Ok. We don&#8217;t need a list of components per manufacturer, but simply a reference from the component to its manufacturer.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Fine, then in Ecore please create a simple reference from class <code>EnergyComponent</code> to class <code>Manufacturer</code>, maybe named <code>producedBy</code>.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Exp</em>: &#8220;I will try this and get back to you.&#8221;</p>
</div>
<div class="paragraph">
<p><em>Dev</em>: &#8220;Fine &#8230;&#8203; good meeting.&#8221;</p>
</div>
</div>
</div>
<div class="paragraph">
<p>Observe in our data model, reference <code>producedBy</code> points <em>from</em> <code>EnergyComponent</code> <em>to</em> <code>Manufacturer</code> making it uni-directional reference.
One can simply query the manufacturer of a product, but not so the other way around.
With a bi-directional reference both queries would be available.</p>
</div>
<div class="paragraph">
<p>Observe also the annotations <code>0..*</code> and <code>1..1</code> near class <code>Manufacturer</code>.
These are <em>multiplicities</em> of associations: An <code>EnergyComponentsCatalog</code> contains zero, one, or many objects of class <code>Manufacturer</code> and an <code>EnergyComponent</code> must reference exactly one manufacturer&#8201;&#8212;&#8201;not less, not more.</p>
</div>
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<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/EcoreRelations.gif" alt="EcoreRelations" width="200">
</div>
<div class="title">Figure 5. Ecore Relations</div>
</div>
<div class="paragraph">
<p>To recapitulate: Our example parameter catalog already exhibits all four types of relations provided by Ecore.
You find these in the Ecore editor&#8217;s palette shown here.
To create a relation between a sub class and a super class use tool <code>SuperType</code>.
Use the other tools to create an association between classes, may it be a simple (uni-directional) reference, a bi-directional reference, or a composition.</p>
</div>
</div>
</div>
<div class="paragraph">
<div class="title">Attributes and Enumerations</div>
<p>Obviously, attributes are central in data modeling.
Create one by dragging it from the palette onto our one and only class so far: <code>EnergyComponentsCatalog</code>.
The class symbol will turn red to indicate an error.
Hover with the mouse pointer over the new attribute and a tooltip with a more or less helpful error message will appear.
Current error is caused by that no data type was set for the new attribute.
Data types for attributes can be integer or floating point numbers, strings, dates, booleans, and more.
To get rid of the error:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>If not already selected, select new attribute by clicking at it in the editor.</p>
</li>
<li>
<p>In view <em>Properties</em> find <code>EType</code> and click button <code>&#8230;&#8203;</code> to see a quite long list of available data types.</p>
</li>
<li>
<p>Choose <code>EString [java.lang:String]</code> from the list and the error is gone.</p>
</li>
</ol>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/EcoreClassWithAttribute.png" alt="EcoreClassWithAttribute" width="200">
</div>
<div class="title">Figure 6. Class with Attribute</div>
</div>
<div class="paragraph">
<p>Change the attribute&#8217;s name to <code>author</code> and the class should look like shown here.</p>
</div>
<div class="paragraph">
<p>Most data types to choose from begin with letter <strong>E</strong> like in <strong>E</strong>core.
These are just Ecore enabled variants of the respective Java types, thus, choose EInt for an int, EFloat for a 32 bit floating point number, EDouble for a 64 bit one, and so on.</p>
</div>
<div class="paragraph">
<p>Ecore allows to introduce new data types.
We employ this feature later to enable data models with physical units and quantities.</p>
</div>
</div>
</div>
<div class="paragraph">
<p>There exists one other means to define the values an attribute can take, namely enumerations of distinct literals. Take <em>Monday</em>, <em>Tuesday</em>, <em>Wednesday</em>, &#8230;&#8203; as a typical example for representing weekdays.
In our example data model you&#8217;ll find one <em>Enumeration</em> named <code>BoilerType</code> with values <code>LowTemperature</code> and <code>Condensing</code>.</p>
</div>
<div class="paragraph">
<div class="title">Homework</div>
<p>The next section deals with generation of Java code from data models. To have more to play with, please implement our example model in Ecore now.</p>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/EcoreClassifier.png" alt="EcoreClassifier" width="200">
</div>
<div class="title">Figure 7. Abstract Class</div>
</div>
<div class="paragraph">
<p>To do this, there is one more thing to know about classes: the difference between ordinary classes and abstract classes.
'Ordinary class' doesn&#8217;t sound nice, therefore, classes that are not abstract are called <em>concrete</em> classes.
Our example diagram depicts abstract classes with letter <strong>A</strong> while concrete classes are labeled with <strong>C</strong>. You add abstract classes to a model with a special palette tool shown here.</p>
</div>
<div class="paragraph">
<p>The thing is: Objects can be created for concrete classes only!</p>
</div>
<div class="paragraph">
<p>In our example, it makes no sense to create an object from class <em>EnergyComponent</em>, because there is not such a thing like an energy component <em>per se</em>.
Therefore, this class is <em>abstract</em>.
It is true that an inverter <em>is</em> an energy component, thus inheriting all its features, but it was <em>created</em> as <em>Inverter</em>, not as <em>EnergyComponent</em>.</p>
</div>
<div class="paragraph">
<p>Super classes will be abstract most of the time.
So my advice is: Model a super class as abstract class unless you convince yourself that there exist real objects in the domain that belong to the super class but, at the same time, do not belong to any of its sub classes.
In the Ecore editor properties view, you can specify if a class is abstract or not, simply by toggling check box <code>Abstract</code>.</p>
</div>
</div>
</div>
<div class="paragraph">
<p>Two more tips and you are ready to rock and roll!&#8201;&#8212;&#8201;At least with your homework.</p>
</div>
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<div class="paragraph">
<p>An exhaustive user manual for Ecore diagram editor is available. Execute <code>Help &#8594; Welcome</code> and follow link <code>Learn how to use the diagram editor</code>.</p>
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<div class="paragraph">
<p>If Ecore models get bigger, you may find it more convenient to work with a form based UI instead of, or in addition to, the diagram editor.
Open this kind of editor via command <code>Open With &#8594; Ecore Editor</code> from the context menu over entry <code>democatalog.ecore</code> in the <em>Model Explorer</em> view.
Note that Eclipse synchronizes different editors of the same content automatically.</p>
</div>
</td>
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<div class="sect2">
<h3 id="truegeneration-of-java-code-from-data-model"><a class="anchor" href="#truegeneration-of-java-code-from-data-model"></a>Generation of Java Code from Data Model</h3>
<div class="paragraph">
<p>By now, your Ecore model should look like this:</p>
</div>
<div id="fig-example-model" class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/Homework.gif" alt="Homework">
</div>
<div class="title">Figure 8. Example Model (Homework)</div>
</div>
<div class="paragraph">
<p>Let us bring the model to life, that is, generate code from it that creates, reads, updates, and deletes concrete data objects of modeled classes in computers.
I would like to tell you that this is done with just one click but, actually, you need two or three:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Make sure all files are saved (<code>File &#8594; Save All</code>)</p>
</li>
<li>
<p>Execute <code>Generate &#8594; Model Code</code> from context menu over <code>democatalog.ecore</code></p>
</li>
<li>
<p>Execute <code>Generate &#8594; Edit Code</code> from context menu over <code>democatalog.ecore</code></p>
</li>
</ol>
</div>
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<p>Please do <strong>not</strong> execute <code>Generate &#8594; All</code> or <code>Generate &#8594; Editor Code</code>.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/GenerateMenu.png" alt="GeneratedClasses" width="260">
</div>
</div>
<div class="paragraph">
<p>This would create code for a simple user interface, but we use more advanced EMF Forms for that later.
If, by mistake, project <code>demo.catalog.editor</code> was created, just delete it from <em>Model Explorer</em> and do not forget to check <code>Delete project contents on disk</code> in confirmation dialog.</p>
</div>
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<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/GeneratedClasses.png" alt="GeneratedClasses" width="260">
</div>
<div class="title">Figure 9. Generated Classes</div>
</div>
<div class="paragraph">
<p><code>Generate &#8594; Model Code</code> creates classes that represent the modeled data in code. These classes are located in three packages under directory <code>src-gen</code> in <code>demo.catalog</code>.</p>
</div>
<div class="paragraph">
<p><code>Generate &#8594; Edit Code</code> creates a whole new Eclipse project named <code>demo.catalog.edit</code>, again with generated classes under directory <code>src-gen</code>.</p>
</div>
<div class="paragraph">
<p>You may have a look at some Java classes for curiosity by double clicking at them in <em>Model Explorer</em>. There is no point in trying to understand the code in detail, but observe token <code>@generated</code> present in the comments of all classes, fields and methods. Classes, fields and methods marked with this token are (re)generated whenever above commands are executed.</p>
</div>
<div class="paragraph">
<p>Sometimes it maybe required to manually adapt generated code&#8201;&#8212;&#8201;after all our concern is "low code", not "no code" development. In that case, we will replace <code>@generated</code> by <code>@generated NOT</code> to prevent code regeneration.</p>
</div>
<div class="paragraph">
<p>After code generation, you may have noticed some warnings showed up in view <em>Problems</em>.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/Warnings.gif" alt="Warnings" width="500">
</div>
<div class="title">Figure 10. Warnings</div>
</div>
<div class="paragraph">
<p>In general, it is highly recommended to resolve warnings, and errors of course, but we will make an exception from the rule, since the warnings are uncritical and would reappear each time code is regenerated.</p>
</div>
</div>
</div>
</div>
<div class="sect2">
<h3 id="truegeneration-and-tweaking-of-user-interface"><a class="anchor" href="#truegeneration-and-tweaking-of-user-interface"></a>Generation and Tweaking of User Interface</h3>
<div class="paragraph">
<p>In this section you will learn how to generate and tweak a CRUD user interface based on Ecore data model and Java classes created for our demo parameters catalog above. Topics described here are discussed in more detail in tutorial <a href="https://eclipsesource.com/blogs/tutorials/getting-started-with-EMF-Forms/">Getting started with EMF Forms</a>.
To find out what user interface controls and layouts are provided by this framework have a look at <a href="https://eclipsesource.com/blogs/tutorials/emf-forms-view-model-elements/">EMF Forms – View Model Elements</a>. <em>EMF Forms</em> is already part of package <em>Eclipse Modeling Tools</em>, so we can create a third Eclipse project/plugin that implements a user interface for editing catalog data without further ado:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>From context menu over <code>democatalog.ecore</code> execute <code>EMF Forms &#8594; Create View Model Project</code></p>
</li>
<li>
<p>Leave project name <code>demo.catalog.viewmodel</code> as is but uncheck <code>Use default location</code>&#8201;&#8212;&#8201;as we always do&#8201;&#8212;&#8201;and browse to the directory containing <code>demo.catalog</code></p>
</li>
<li>
<p>Click <code>Next &gt;</code> and select <code>EnergyComponentsCatalog</code> as data element we want to create a user interface for</p>
</li>
<li>
<p>Leave <code>Fill view model with default layout</code> checked and click <code>Finish</code>.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>According to these inputs a new project is created with file <code>EnergyComponentsCatalog.view</code> under directory <code>view models</code>.
This file opens automatically in a special <em>View Editor</em>.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModel.png" alt="ViewModel1">
</div>
<div class="title">Figure 11. New View Model</div>
</div>
<div class="paragraph">
<p>Like the <strong>data</strong> of our catalog are modeled as Ecore file using a dedicated graphical editor, so will our catalog’s <strong>user interface</strong> be modeled in <code>.view</code> files, again using a special editor.</p>
</div>
<div class="paragraph">
<p>Since we opted for <code>Fill view model with default layout</code> the catalog&#8217;s UI is filled initially with default controls for all data items assigned to Ecore type <code>EnergyComponentsCatalog</code> like a string control for <code>author</code> or list controls for <code>boilers</code>, <code>chps</code>, and so on.</p>
</div>
<div class="paragraph">
<p>See red arrow in the above screen-shot?
It points to a button that opens a functional preview of the modeled user interface.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewEditorPreview.png" alt="ViewModel1" width="500">
</div>
<div class="title">Figure 12. User Interface Preview</div>
</div>
<div class="admonitionblock tip">
<table>
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<td class="icon">
<i class="fa icon-tip" title="Tip"></i>
</td>
<td class="content">
<div class="paragraph">
<p>Double click on tab <em>EMF Forms Preview</em> to enlarge view for better handling&#8201;&#8212;&#8201;double click again to get back.</p>
</div>
<div class="paragraph">
<p>Enable auto refresh mode <span class="image"><img src="ParameterCatalogs2Images/ViewModelAutomaticRefresh.gif" alt="ViewModelAutomaticRefresh" width="40"></span> to let each change in the view model instantly be reflected in the preview.</p>
</div>
<div class="paragraph">
<p>Given your screen is big enough, you may want to dock-out the preview by dragging tab <em>EMF Forms Preview</em> out of Eclipse&#8217;s main window.
Seeing editor and preview side by side is a great way to explore the possibilities of view models.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>Red input field and exclamation mark in the preview signal missing or inconsistent data.
Ecore data model specifies attribute <code>author</code> with a lower bound of one, meaning it is a mandatory attribute.
As soon as an author&#8217;s name is provided, the error indication disappears.
This is what <em>functional</em> preview means.
You can even create new boilers or other objects in lists provided, with all forms created "automagically" with respect to our underlying Ecore data model.</p>
</div>
<div class="paragraph">
<p>Of course, such automatic approach has its limits.
In our case, to have a long list of lists is not very user-friendly, because one has to scroll up and down to find a specific list.
Also, no specific object data are shown in the list and data can only be edited in a pop-up form (no inline editing).</p>
</div>
<div class="paragraph">
<p>How should a better UI look and feel like?</p>
</div>
<div class="paragraph">
<p>If there are many lists (types) of entities&#8201;&#8212;&#8201;the normal case for parameter catalogs&#8201;&#8212;&#8201;users should select what list they want to work with by selecting it from a list or tree view that is always visible, the <em>master view</em>.
Once a type is selected in the master view, a table with all objects of this list/type shall appear sidelong in a <em>detail view</em>, ready for editing.</p>
</div>
<div class="paragraph">
<p>In <em>EMF Forms</em> master-detail-views can be modeled either with <em>Categorization</em> or <em>Tree Master Detail</em> UI components.
The latter not only allows to edit information displayed in the detail view, but also the tree of elements in the master view.
Opposed to that, a <em>Categorization</em> presents a fixed hierarchy of elements to choose from.
This is exactly what we need as there are only a fixed number of types of objects to be edited in a parameters catalog.</p>
</div>
<div class="sect3">
<h4 id="trueadding-tables-to-the-ui"><a class="anchor" href="#trueadding-tables-to-the-ui"></a>Adding Tables to the UI</h4>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelDeleteControls.gif" alt="ViewModelDeleteControls" width="300">
</div>
<div class="title">Figure 13. Delete default list controls</div>
</div>
<div class="paragraph">
<p>But first, we replace the default controls for lists of boilers, chps, and so on by tables. As shown here, select all list controls in the view model and execute <code>Delete</code> from context menu. Refresh <em>View Editor Preview</em> to verify that only field <code>Author*</code> is left.</p>
</div>
</div>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelCreateTable.gif" alt="ViewModelCreateTable" width="300">
</div>
<div class="title">Figure 14. Create Table Control</div>
</div>
<div class="paragraph">
<p>Next, create a table that shall display all boilers in a catalog:
Select <code>EnergyComponentsCatalog</code>, activate context menu and choose <code>TableControl</code> from the list of available UI elements.
(EnergyComponentsCatalog represents the root view of the UI and, as such, accepts quite a lot of different UI components as child components.)</p>
</div>
<div class="paragraph">
<p>Entry <code>TableControl</code> was inserted into the list of interface elements below <code>Control author</code>.
Checking updated preview reveals no table but a message basically saying that a reference to the domain model is missing, in other words: <em>EMF Forms</em> does not know yet what data to present in table.
Click on entry <code>TableControl</code> to see its details.
A red exclamation mark indicates the missing <code>Domain Model Reference*</code>.
Click on <span class="image"><img src="ParameterCatalogs2Images/ButtonLinkPlus.gif" alt="ButtonLinkPlus" width="40"></span> and be ready to chase a sequence of dialogs:</p>
</div>
</div>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Click on another <span class="image"><img src="ParameterCatalogs2Images/ButtonLinkPlus.gif" alt="ButtonLinkPlus" width="40"></span> in dialog <code>Configure TableDomainModelReference</code></p>
</li>
<li>
<p>In wizard <code>New Reference Element</code> select <code>model &#8594; FeaturePathDomainModelReference</code> and click <code>Next &gt;</code></p>
</li>
<li>
<p>Click <code>Link Domain Model EFeature</code> and in appearing pop-up list choose reference to list of objects you want to edit in the table, e.g. <code>boilers</code>; confirm with <code>OK</code> safely ignoring warning about missing <code>PropertyDescriptor</code>.</p>
</li>
<li>
<p><code>Finish</code> wizard <code>New Reference Element</code></p>
</li>
<li>
<p><code>Finish</code> dialog <code>Configure TableDomainModelReference</code>.</p>
</li>
</ol>
</div>
<div class="paragraph">
<p>This was some work, but as reward we get a fully specified table control in <em>View Editor</em> that "translates" into a preview where we can create, read, update, and delete boilers.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelWithTable.gif" alt="ViewModelWithTable.gif">
</div>
<div class="title">Figure 15. Table for Boilers</div>
</div>
<div class="paragraph">
<p>Moreover, clicking at a table header sorts all objects in it (rows) according to the values in this column.
Column widths can adapted, too.</p>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelTweakTable.gif" alt="ViewModelTweakTable" width="300">
</div>
<div class="title">Figure 16. Modify Table Control</div>
</div>
<div class="paragraph">
<p>Table UIs can be tweaked in many ways, e.g. selection and sequence of columns can be declared via list <code>Column Domain Model References</code>. To fill this list with defaults, execute <code>Generate Columns</code> from table control&#8217;s context menu. Reorder them as you like or delete columns that are not important to the user.</p>
</div>
<div class="paragraph">
<p>Notice here an important overall feature of <em>EMF Forms</em>: If something is left unspecified, be it the view model for an Ecore object type or the specification of table columns, <em>EMF Forms</em> will always find a default solution! Applied to columns specification this means we get default columns automatically back in the moment the last column is removed from list <code>Column Domain Model References</code>.</p>
</div>
<div class="paragraph">
<p>If explicit column specifications are present further configurations can be added to a table control from its context menu, e.g. initial column widths or read-only status of columns. See <a href="https://eclipsesource.com/de/blogs/2018/01/31/emf-forms-1-15-0-feature-enhanced-table-renderer/">here</a> for details.</p>
</div>
</div>
</div>
<div class="paragraph">
<p>By default only attributes are displayed and directly editable in tables while references to other objects&#8201;&#8212;&#8201;in our case the reference to a manufacturer&#8201;&#8212;&#8201;are not.</p>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelWithPanel.gif" alt="ViewModelWithPanel" width="300">
</div>
<div class="title">Figure 17. Default Panel for Boilers</div>
</div>
<div class="paragraph">
<p>To get the default (<em>sic!</em>) editing panel for an selected table row, in <em>View Editor</em> just set <code>Detail Editing*</code> from <code>None</code> to <code>WithPanel</code>, <strong>press <em>Tab</em></strong>, and save. For boilers, <em>EMF Forms</em> will create the editing panel shown here. Regardless wether users edit data in the panel or directly in the table&#8201;&#8212;&#8201;both will stay in sync any time.</p>
</div>
</div>
</div>
<div class="admonitionblock warning">
<table>
<tr>
<td class="icon">
<i class="fa icon-warning" title="Warning"></i>
</td>
<td class="content">
<div class="paragraph">
<p><em>View editor</em> exhibits an irritating behavior: With preview auto-refresh turned on, any change in the details view is reflected instantly in the preview, even without saving the form or leaving the edited field.</p>
</div>
<div class="paragraph">
<p>On the other hand, <strong>saving</strong> an updated view editor only takes into account edited fields after they have lost focus, e.g. by pressing <em>Tab</em> key or clicking with the mouse into another field.
So, saving a form before the focus has shifted from the last edited field won&#8217;t honor this edit, that is you won&#8217;t necessarily get what you see.</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>One last thing: Enter <code>boilers</code> as name for the table control so we can distinguish it from the other four table controls to come.</p>
</div>
<div class="paragraph">
<p>Yes! &#8230;&#8203; Please repeat above procedure to create table controls for chps, solar panels, inverters and manufacturers, too. I did this in about 3 minutes. ;-)</p>
</div>
</div>
<div class="sect3">
<h4 id="truemaster-detail-view-with-categories"><a class="anchor" href="#truemaster-detail-view-with-categories"></a>Master-Detail View with Categories</h4>
<div class="paragraph">
<p>In last section we improved our catalog&#8217;s UI by replacing simple object lists by tables that can be sorted, customized and edited inline as well as in an associated panel.
Alas, instead a list of lists we have got an even bigger list of tables.</p>
</div>
<div class="paragraph">
<p>High time to introduce a master-detail view that presents categories of object types in a master view and, after one is selected, the according object table as detail.</p>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelCatgorization1.gif" alt="ViewModelCatgorization1" width="180">
</div>
<div class="title">Figure 18. Category Tree</div>
</div>
<div class="paragraph">
<p>Add a <em>Categorization</em> view to the list of UI elements in <em>View Editor</em> by selecting <code>EnergyComponentsCatalog</code> and choose <code>Categorization</code> from its contect menu.</p>
</div>
<div class="paragraph">
<p>Now add two <code>Composite Category</code> elements and one <code>Leaf Category</code> to <code>Categorization</code> from according context menu. This gives us three top level entries in the hierarchy.</p>
</div>
<div class="paragraph">
<p>In the same way add two <code>Leaf Category</code> elements to each <code>Composite Category</code> resulting in the hierarchy depicted here.</p>
</div>
</div>
</div>
<div class="openblock float-group">
<div class="content">
<div class="imageblock right thumb">
<div class="content">
<img src="ParameterCatalogs2Images/ViewModelCatgorization2.gif" alt="ViewModelCatgorization2" width="260">
</div>
<div class="title">Figure 19. Completed View Model</div>
</div>
<div class="paragraph">
<p>This screen shot shows the view model of our UI when finished. To get there:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Select UI element <code>Categorization</code> and rename it to <code>Categories</code></p>
</li>
<li>
<p>Rename composite and leaf categories as depicted here</p>
</li>
<li>
<p>Drag all table controls one by one into the suited leaf category</p>
</li>
<li>
<p>Confirm master-detail view works as expected in the preview.</p>
</li>
</ol>
</div>
</div>
</div>
<div class="admonitionblock important">
<table>
<tr>
<td class="icon">
<i class="fa icon-important" title="Important"></i>
</td>
<td class="content">
<div class="paragraph">
<p>The UI hierarchy to access tables for entity types is independent, and usually will differ, from aggregation and inheritance hierarchies present in Ecore data model (compare fig. <a href="#fig-example-model">Example Model</a>).</p>
</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>Note that <em>EMF Forms Preview</em> provides these buttons <span class="image"><img src="ParameterCatalogs2Images/ViewModelPersistence.gif" alt="PreviewPersistanceButtons" width="68"></span> to clear, load and store edited data.
In fact, this feature gives us a fully functional prototype.
At least during refinement of model and UI, data sets can be created, edited, and tested for usability without the need to built a full blown, deployable application&#8201;&#8212;&#8201;see parts <em>Accessing and Using Parameter Catalogs</em> and <em>Build (Parameter Catalog) Applications with Eclipse Tycho</em> below.</p>
</div>
<div class="paragraph">
<p>Be aware that in some cases the view model must adapt to changes in the data model, e.g. a new leaf category and table component has to be created for a new catalog object type.
Other changes are automatically reflected in the generated UI, at least for default forms and other UI elements.
To our convenience, view model specifications incompatible with data model are indicated by error badges in the <em>View Editor</em>.</p>
</div>
<div class="paragraph">
<p>Changes in data model also can make existing XML data incompatible. There are tools for data migration, but for now, recreation of test data or manual editing of XML file is the way to go.</p>
</div>
</div>
<div class="sect3">
<h4 id="truesummary"><a class="anchor" href="#truesummary"></a>Summary</h4>
<div class="paragraph">
<p>What have we achieved so far?</p>
</div>
<div class="paragraph">
<p>We created a graphical Ecore data model with a catalog class and five classes/types of objects therein.
Classes have been defined by name, attributes, and relations between, often with cardinalities.
Whenever classes shared some attributes or references we factored these out into super classes.
An enumeration introduced a new attribute type from a set of named values.</p>
</div>
<div class="paragraph">
<p>From this data model, we issued commands to create matching Java code for representing the data in memory as well as to store and retrieve them on and from disk. Methods to create, read, update and delete data objects (CRUD) were generated, too.</p>
</div>
<div class="paragraph">
<p>Lastly, we thought about a good user interface for this data and used <em>EMF Forms</em> to model and prototype it.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="truebonus-solutions-for-specific-modeling-problems"><a class="anchor" href="#truebonus-solutions-for-specific-modeling-problems"></a>Bonus: Solutions for Specific Modeling Problems</h3>
<div class="sect3">
<h4 id="trueadd-units-to-the-mix"><a class="anchor" href="#trueadd-units-to-the-mix"></a>Add Units to the Mix</h4>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<p>As mentioned earlier, parameter catalogs for simulations should be able to represent quantities, not just bare integer and real numbers.</p>
</div>
<div class="paragraph">
<p>using Indrya, the reference implementation for Units of Measurement in Java (JSR 385)</p>
</div>
<div class="paragraph">
<p>To this end, the author has created two Eclipse plug-in projects providing this feature to be used by Ecore and EMF Forms.</p>
</div>
<div class="paragraph">
<p>Third-party libraries like Indrya, usually, are not distributed as plug-ins, but <em>Tycho</em> can wrap them automatically as OSGi plug-ins that can added directly to our application.</p>
</div>
<div class="paragraph">
<p>Another plug-in, created by the author connects the Ecore and Indrya. We will compile it from source code, simply by importing the projects.</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Copy to file system &#8230;&#8203;</p>
</li>
<li>
<p>Import project but <strong>not</strong> copying it in the workspace (just linking)</p>
</li>
</ol>
</div>
</div>
<div class="sect3">
<h4 id="truerepresent-functions-in-a-parameter-catalog"><a class="anchor" href="#truerepresent-functions-in-a-parameter-catalog"></a>Represent Functions in a Parameter Catalog</h4>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<p>for creating custom UI labels:</p>
</div>
<div class="ulist">
<ul>
<li>
<p><code>ExponentialFunctionItemProvider.java</code></p>
</li>
<li>
<p><code>LinearFunctionItemProvider.java</code></p>
</li>
<li>
<p><code>TableFunctionItemProvider.java</code></p>
</li>
</ul>
</div>
<div class="paragraph">
<p>Custom code marked with <code>@generated NOT</code> in <code>de.hftstuttgart.energycomponents.provider</code> in project <code>de.hftstuttgart.energycomponents.edit</code></p>
</div>
</div>
<div class="sect3">
<h4 id="truehow-to-model-derived-references-and-attributes"><a class="anchor" href="#truehow-to-model-derived-references-and-attributes"></a>How to Model Derived References and Attributes</h4>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<p>We haven&#8217;t used derived references or attributes by now. But if one has to implement some by providing a getter, it is necessary to return an unmodifiable list like BasicEList.UnmodifiableEList or EcoreUtil.unmodifiableList(&#8230;&#8203;) instead of EList as described here: <a href="https://www.ntnu.no/wiki/plugins/servlet/mobile?contentId=112269388#content/view/112269388" class="bare">https://www.ntnu.no/wiki/plugins/servlet/mobile?contentId=112269388#content/view/112269388</a> .</p>
</div>
<div style="page-break-after: always;"></div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="trueaccessing-and-using-parameter-catalogs"><a class="anchor" href="#trueaccessing-and-using-parameter-catalogs"></a>Accessing and Using Parameter Catalogs</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="trueaccessing-xml-catalogs"><a class="anchor" href="#trueaccessing-xml-catalogs"></a>Accessing XML-Catalogs</h3>
<div class="paragraph">
<div class="title">Add Ecore data model to a third-party Java application</div>
<p><strong>TBD</strong></p>
</div>
<div class="literalblock">
<div class="content">
<pre>import java.util.Collection;
import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.resource.ResourceSet;
import org.eclipse.emf.ecore.resource.impl.ResourceSetImpl;
import org.eclipse.emf.ecore.util.EcoreUtil;
import de.hftstuttgart.energycomponents.EnCompPackage;
import de.hftstuttgart.energycomponents.HeatPump;</pre>
</div>
</div>
<div class="literalblock">
<div class="content">
<pre>ResourceSet resSet = new ResourceSetImpl();
Resource resource = resSet.getResource(URI.createURI("catalog.xml"), true);
Collection&lt;HeatPump&gt; allHeatPumps = EcoreUtil.getObjectsByType(
resource.getContents(), EnCompPackage.eINSTANCE.getHeatPump());</pre>
</div>
</div>
<div class="paragraph">
<p>catalog.xml muss durch den richtigen Pfad zum XML-Katalog ersetzt werden.</p>
</div>
<div class="paragraph">
<div class="title">Load XML Data Catalog and Access Corresponding Java Objects in Code</div>
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<div class="title">Access from Python?</div>
<p><strong>TBD</strong></p>
</div>
</div>
<div class="sect2">
<h3 id="truecreate-insel-models-with-handlebars-templates"><a class="anchor" href="#truecreate-insel-models-with-handlebars-templates"></a>Create Insel Models with Handlebars Templates</h3>
<div class="paragraph">
<p>Handlebar templates to access data catalogs and create/parameterize textual simulation models.</p>
</div>
<div class="paragraph">
<div class="title">Parameterization of blocks</div>
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<div class="title">Creation of submodels, e.g. computing parameterized functions</div>
<p><strong>TBD</strong></p>
</div>
<div style="page-break-after: always;"></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="truebuild-parameter-catalog-applications-with-eclipse-tycho"><a class="anchor" href="#truebuild-parameter-catalog-applications-with-eclipse-tycho"></a>Build (Parameter Catalog) Applications with Eclipse Tycho</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Three plugins so for for the content and UI.</p>
</div>
<div class="paragraph">
<p>Missing: Deployable application and inclusion to third party libraries.</p>
</div>
<div class="paragraph">
<p>Building an application "around" the three plugins for Ecore data model and UI specification model.</p>
</div>
<div class="paragraph">
<p>See template.</p>
</div>
<div class="sect2">
<h3 id="truecreate-an-eclipse-application"><a class="anchor" href="#truecreate-an-eclipse-application"></a>Create an Eclipse Application</h3>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
</div>
<div class="sect2">
<h3 id="trueuse-maven-and-tycho-as-build-system"><a class="anchor" href="#trueuse-maven-and-tycho-as-build-system"></a>Use Maven and Tycho as Build System</h3>
<div class="paragraph">
<div class="title">Install Maven Support</div>
<p>We are going to create a complete Eclipse desktop application from generated code.
We also want to deploy this application for Linux, macOS and Windows operating systems.
Eclipse offers several approaches for compiling and deploying such an application, traditionally with <em>Ant</em> scripts.</p>
</div>
<div class="paragraph">
<p>Creation and maintenance of these scripts turned out to be tedious and error prone.
For quite some years now, the proposed&#8201;&#8212;&#8201;and mostly supported&#8201;&#8212;&#8201;method for building Eclipse applications is to use <em>Maven</em> build system, more specifically, a couple of Maven plug-ins, subsumed under the name <em>Tycho</em>.</p>
</div>
<div class="paragraph">
<p>Many Eclipse platforms have Maven support <a href="https://www.eclipse.org/m2e/"><em>M2Eclipse</em></a> already built in, not so our <em>Eclipse Modeling Tools</em>.
But don&#8217;t worry: Installation of required Eclipse feature is easy and straight forward.
And, by the way, you will acquire the indispensable skill of how to install new plug-ins/features to Eclipse.</p>
</div>
<div class="paragraph">
<p>First, tell your Eclipse installation where to look for the new software.
Execute <code>Help &#8594; Install new Software&#8230;&#8203;</code> to invoke dialog <em>Available Software</em> and press <code>Add&#8230;&#8203;</code>.
Sub-dialog <code>Add Repository</code> pops up.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/InstallMaven1.gif" alt="InstallMaven1">
</div>
<div class="title">Figure 20. Add update site m2e</div>
</div>
<div class="paragraph">
<p>In there provide <code>m2e</code> as name and</p>
</div>
<div class="literalblock">
<div class="content">
<pre>http://download.eclipse.org/technology/m2e/releases</pre>
</div>
</div>
<div class="paragraph">
<p>as location.
After confirmation with <code>Add</code>, Eclipse now looks up the site for available software.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/InstallMaven2.gif" alt="InstallMaven2">
</div>
<div class="title">Figure 21. Choose features to install</div>
</div>
<div class="paragraph">
<p>Check the items to install like shown above and confirm all following questions about licenses and security concerns.
After download is complete&#8201;&#8212;&#8201;it can take a few minutes&#8201;&#8212;&#8201;restart Eclipse.
Verify that Maven version 3.6.3 or above is now installed in <code>Window &#8594; Preferences&#8230;&#8203;</code> (or <code>Eclipse &#8594; Preferences&#8230;&#8203;</code> on macOS) under <code>Maven &#8594; Installations</code>.</p>
</div>
<div class="imageblock thumb">
<div class="content">
<img src="ParameterCatalogs2Images/InstallMaven3.gif" alt="InstallMaven3" width="400">
</div>
<div class="title">Figure 22. Check Maven installation</div>
</div>
<div class="paragraph">
<div class="title">"Mavenize" projects</div>
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<div class="title">Build and Deploy with Tycho</div>
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<div class="title">Add third party Java libraries</div>
<p><strong>TBD</strong></p>
</div>
<div class="paragraph">
<p>"Correct" way to add third party Java libraries as plugins</p>
</div>
<div class="paragraph">
<p>Example Indriya</p>
</div>
</div>
<div class="sect2">
<h3 id="truedeploy-to-p2-repository"><a class="anchor" href="#truedeploy-to-p2-repository"></a>Deploy to P2 Repository</h3>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
</div>
<div class="sect2">
<h3 id="trueversioning-and-collaboration"><a class="anchor" href="#trueversioning-and-collaboration"></a>Versioning and Collaboration</h3>
<div class="paragraph">
<p><strong>TBD</strong></p>
</div>
</div>
</div>
</div>
</div>
<div id="footnotes">
<hr>
<div class="footnote" id="_footnotedef_1">
<a href="#_footnoteref_1">1</a>. A similar approach is in use to standardize extensions to CityGML via so called application domain extensions (ADE) like the energy ADE for exchanging energy related data.
</div>
<div class="footnote" id="_footnotedef_2">
<a href="#_footnoteref_2">2</a>. A comparable, but completely different approach would be to combine several web applications and services via portal software in web browsers.
</div>
<div class="footnote" id="_footnotedef_3">
<a href="#_footnoteref_3">3</a>. The notion of an Eclipse package has nothing to do with Java packages.
</div>
<div class="footnote" id="_footnotedef_4">
<a href="#_footnoteref_4">4</a>. Projects possess one or more <em>natures</em> used to define a project&#8217;s principal type.
</div>
<div class="footnote" id="_footnotedef_5">
<a href="#_footnoteref_5">5</a>. Or even work on the same workspace provided in the cloud, see <a href="https://www.eclipse.org/che/technology/">Eclipse Che</a>.
</div>
<div class="footnote" id="_footnotedef_6">
<a href="#_footnoteref_6">6</a>. AdoptOpenJDK recently joined the Eclipse foundation and soon will change its name to <em>Adoptium</em> for legal reasons.
</div>
<div class="footnote" id="_footnotedef_7">
<a href="#_footnoteref_7">7</a>. Please stay away from version 2020-03 and 2020-06 of Eclipse Modeling Tools, since these came with a bug preventing the user from editing data in table cells within the generated UI.
</div>
</div>
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<div id="footer-text">
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== Introduction
[IMPORTANT]
====
This introduction talks about the work of the author and others, but without bibliographic references. Currently, it is just meant as background to better understand the technical documentation in the sections to follow.
Maybe it could be developed into a more serious paper later.
====
The overall motivation for the work on parameter catalogs for simulation is to make easier to develop and perform computer simulations in complex and _data rich_ domains like building physics, transportation, and all kinds of urban infrastructure.
=== The Bigger Picture
A good part of computer science was and is driven by the motivation to make it easier to develop computer programs of all sorts.
"Higher" programming languages were invented to make programs human readable and soon special constructs for _functional programming_ (computation without side effects) and _structured programming_ (computation without go to statements) were introduced to help programmers writing and understanding ever growing programs.
Then, between 1962 and 1967, program language Simula was developed especially to deal with the challenges of simulating systems comprising of many different types of objects.
This opened the door to more direct computer representations of real world objects, their attributes, relationships and behavior, ultimately leading to _object-oriented_ software development that today is embodied in programming languages like Java, C++, Python, and graphical notations like the Unified Modeling Language (UML).
While these achievements had boosted the productivity of software developers, still the creation of correct, efficient and maintainable programs -- including simulations -- required a big deal of expert knowledge and experience.
To overcome this bottleneck, starting in the 70s, so called 4th generation languages entered the stage.
These languages were tailored to specific tasks like statistics ("S" 1976, "R" being its successor), database programming (SQL 1979), or simulation (MATLAB around 1979, Mathematica 1988, Modellica 1999) to name a few.
By sacrificing generality, these special languages become more accessible to domain experts, not just trained software developers.
To flatten the learning curve even more, formal _graphical_ languages for special purposes were invented, e.g. Simulink for block diagram simulation models in 1984, Entity-Relationship-Diagrams for data modeling in 1976, UML for object-oriented systems design in the 1990s, or graphical languages to specify business and also scientific workflows around 2000.
This very short history of technologies for development of software in general, and simulations in particular, shall illuminate the tools at our disposal:
* general purpose programming languages that combine structured, functional and object-oriented approaches to enable the creation of big, modular software systems, often called "programming in the large"
* formal textual domain specific languages (DSLs) dedicated to solve specific tasks with ease
* formal graphical DSLs.
====
Note that DSLs more tend to describe _what_ shall be achieved by a computation instead of describing in detail, _how_ to achieve it.
Therefore, DSLs usually look more like a model than like an algorithm.
====
Now back to the task at hand.
Some domains deal with a few types of simple objects to be simulated.
Take the building blocks of an electric circuit as an example.
The algorithms to simulate these correctly and efficiently may be quite complex -- the model elements usually can be described by very few parameters like resistance or capacity.
More complex domains like (regenerative) energy systems or building physics deal with more complex objects to be simulated, e.g. PV modules or layered walls of buildings, often coming in different types and configurations, and dozens of possibly interdependent parameters.
=== Lessons Learned
First a note on terminology: Instead of _parameter catalogs_ in SimStadt we used term _library_ like in _building physics library_. Obviously this was not a good choice, since _library_ is used a lot in IT and programming with all sorts of meaning. Instead we started to talk about _data catalogs_, but in data science this term has specific meaning, namely: catalogs of data and data sources.
Since our catalogs, first of all, shall grant structured access to parameters for simulated entities _parameter catalog_ sounds more appropriate to me.
The problem of navigating huge parameter spaces and assembling complex simulation models popped up as the author worked on a diagram editor for *INSEL*, a simulation language and runtime environment developed for renewable energy systems simulation.
To make existing catalogs on weather data, solar panels and inverter modules accessible to the modeler, special dialogs were added to the INSEL user interface that allowed browsing through the catalogs.
Using this browsers, the modeler would choose a weather station, panel or inverter to parameterize a corresponding INSEL function-block.
However, there are some severe disadvantages with this approach:
. Parameter catalogs were stored in a proprietary data format on disk within the INSEL application distribution, meaning they could not used independently from INSEL by other interested parties (systems or users).
. The catalogs have to be maintained by editing text files manually.
. While INSEL modeler could browse the catalogs, searching and sorting were not supported.
. Development of Java Swing UIs for the different kind of catalogs is time consuming as is their maintenance, e.g. if a catalog data format were to change.
. Putting UIs to handle big amounts of data into a diagram editor is not very user friendly.
From 2013 to 2016, the simulation platform *SimStadt* was developed to make specific modeling and simulation workflows accessible to experts in urban planning and energy systems.
Using INSEL and other simulators under the hood, the usage of 3D city data, provided as CityGML files, was a core requirement of this project.
To enable simulation of, say, the heating demand of a district, geometric building data had to be enriched with data on building physics and usage.
To do so, existing informations about building physics and usage -- often only available as informal typologies or tables -- had to be provided to the SimStadt user on an abstract level, e.g. to choose between refurbishment scenarios.
At the same time, specific building configurations and parameter sets had to be injected into the simulation models to obtain the desired results.
Again, we implemented parameter catalogs to fulfill these requirements, but compared to the quite simple catalogs used in INSEL, the data for building materials, window, wall and roof types as well as the typologies of buildings, households, usage patterns, and so on were more intricate.
They had to be created iteratively in collaboration with domain experts.
In this situation, manual coding data formats and access with a general programming language would have led to relatively long iteration cycles and high communication effort between programmer and domain expert.
Instead, we decided to use a DSL for data modeling and use code generation whenever possible.
Since SimStadt was developed within the Java eco-system we followed this standard approach:footnote:[A similar approach is in use to standardize extensions to CityGML via so called application domain extensions (ADE) like the energy ADE for exchanging energy related data.]
. Developer and domain expert create a first version of the data model as XML Schema Definition (our DSL).
. For plausibility checks one would use any standard XML editor to create example data conforming to the XSD.
. With JAXB (Java Architecture for XML Binding) Java code is generated to read our XML catalogs into Java objects that, in turn, can be accessed by SimStadt workflows to generate and parameterize simulations.
. If required, developer and domain expert go back to step one to refine data model and catalog data.
After the data model for building physics catalogs had matured, we developed a desktop application for convenient creation and maintenance of building physics data catalogs separate from SimStadt.
It was developed in Java with a user interface written in JavaFX and was well received by domain experts.
However, as a different catalog -- this time for building usages -- had to be created, it was quite difficult to reuse the XML schema and application code from the building physics catalog: The usage catalog data model was "pressed" into a form similar to the building physics catalog data model, and the UI code was "over-engineered" to accommodate both catalog's requirements.
=== Low-Code-Development of Parameter Catalogs
From INSEL and SimStadt we learned, that manual and automatic construction and parameterization of complex simulation models with many types of interrelated objects should be supported be the means of domain specific parameter catalogs.
Close collaboration with domain experts in designing and implementing these catalogs in short development cycles is desirable.
Parameter catalogs and the software for their creation, maintenance and deployment should be independent of any specific simulation software, (a) to be reusable and (b) not to overload simulation applications.
In SimStadt, catalog development was partly facilitated by a textual DSL for data modeling (XML schema language) and automatic generation of Java code from it.
On the other hand, user interfaces and generation and parameterization of simulations from templates within SimStadt workflows had still to be coded manually hindering the routinely creation of new catalogs.
Now, in 2020, several developments in different projects provide an opportunity to re-think the topic of parameter catalogs for simulations, namely:
. Plans for a new Urban Simulation Platform at Concordia University, Montreal.
. New implementation of INSEL user interface based on the Eclipse application framework and Eclipse-Sirius diagram editors.
. Enhancement of existing building physics and usage catalogs from SimStadt and their adaptation to new regions.
. Development of a new comprehensive catalog of electric systems components to be used in SimStadt as well as in Concordia's Urban Simulation Platform.
====
In what follows, the new technology stack used to implement (4) is documented in detail.
It uses four technologies to replace manual coding by code generation from models:
* _Ecore_ to model the catalog's data and generate Java classes and persistence layer from it.
* _EMF Forms_ for modeling and generating tables, forms and buttons to **c**reate, **r**ead, **u**pdate, and **d**elete data (CRUD).
* _E4_, the Eclipse way of modeling the application user interface itself, e.g. the placement and behavior of views, editors, toolbars, menus, and more.
* A template engine called _Handlebars_ to generate fully parameterized simulation models from textual templates without programming.
The new technology stack is rooted in the Eclipse application framework and eco-system.footnote:[A comparable, but completely different approach would be to combine several web applications and services via portal software in web browsers.]
Its main advantage is the possibility to implement CRUD applications like parameter catalogs and their underlying data models with no or very view lines of handwritten code (_low-code-development_).
====
Plans are to use the same approach also for implementation of (3).
Since task (2) and maybe (1) will use Eclipse, too, close integration of parameter catalogs and simulation environments seems feasible.
E.g., a user could drag an electric system component from a catalog onto an INSEL block for parametrization.
The Eclipse application framework offers:
* OSGI plug-in mechanism and UI framework for integrating applications and services
* _E4_ application model to declaratively describe user interface's structure
* General notion of _project_ with specific file types, help system, preferences etc.
* IDE support for important general purpose languages like Java, https://marketplace.eclipse.org/content/pydev-python-ide-eclipse[Python], Ruby, C, Fortran, C++
* Support for creating textual and graphical DSLs (https://www.eclipse.org/Xtext[XText], https://www.eclipse.org/sirius[Sirius])
* Industry proven DSLs and code generators for data models and form based UIs via the https://www.eclipse.org/modeling/emf[_Eclipse Modeling Framework_] (EMF) providing:
** https://www.eclipse.org/ecoretools[_Ecore_] for model driven generation of Java classes and persistence layers for XML or data bases
** https://eclipsesource.com/blogs/tutorials/emf-forms-view-model-elements[_EMF Forms_] for describing and generating form based UIs
** Mechanisms to adapt or extend data models and forms to special needs (e.g., we added quantities -- that is numbers _with units_ -- to Ecore and EMF Forms, a feature very important for parameter catalogs)
* Rich open source eco-system with lots of plugins and projects important for an urban simulation platform:
** model server for distributed access and work on Ecore models, including model comparison and migration (https://projects.eclipse.org/projects/modeling.emf.cdo[CDO], https://www.eclipse.org/emf/compare[EMFCompare])
** a https://pyecore.readthedocs.io/en/latest[Python implementation of Ecore]
** GIS: storage, processing, and visualization of geographical data (list of projects under the umbrella https://projects.eclipse.org/projects/locationtech[LocationTech], e.g. user-friendly desktop internet GIS http://udig.refractions.net[uDig])
** workbench for traffic simulation (https://www.eclipse.org/sumo[SUMO])
** spatial multi-agent-simulation (https://gama-platform.github.io/wiki/Home[GAMA-Platform])
** scientific workflows (https://projects.eclipse.org/projects/science.triquetrum[Triquetrum])
** visualizations (https://www.eclipse.org/nebula/widgets/visualization/visualization.php[Nebula])
** machine learning (https://deeplearning4j.org[deeplearning4j])
** 45+ projects in the area of https://iot.eclipse.org[IoT]
** ...
As always, all that glitters is not gold. When we go through the details below, some bugs and inconsistencies, typical for open source projects of this age and size, have to be addressed.
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== How to Implement Parameter Catalogs with Eclipse
:imagesdir: ParameterCatalogs2Images
To build a new parameter catalog from scratch, we first have to understand some basics about Eclipse, and then install the correct Eclipse package.
Thereafter, we can model our data with Ecore considering some best practices, followed by the generation of Java classes and user interface (UI).
We, then, will add some plug-ins to "pimp" our Eclipse installation, (a) to enable deployment of parameter catalog applications, and (b) to add units and quantities to the mix.
Some hints on special modeling problems and versioning parameter catalogs conclude this how-to guide.
=== Eclipse Basics
https://en.wikipedia.org/wiki/Eclipse_(software)[Eclipse] was originally developed by IBM and became Open Source in 2001.
It is best known for its Integrated Development Environments (_Eclipse IDEs_), not only for Java, but also for C++, Python and many other programming languages.
These IDEs are created on top of the Eclipse Rich Client Platform (Eclipse RCP), an application framework and plug-in system based on Java and OSGi.
Eclipse RCP is foundation of a plethora of general-purpose applications, too.
First time users of Eclipse better understand the following concepts.
.Eclipse Packages
An Eclipse package is an Eclipse distribution dedicated to a specific type of task.footnote:[The notion of an Eclipse package has nothing to do with Java packages.]
A list of packages is available at https://www.eclipse.org/downloads/packages/[eclipse.org].
Beside others it contains _Eclipse IDE for Java Developers_, _Eclipse IDE for Scientific Computing_, and the package we will use: _Eclipse Modeling Tools_.
Note that third parties offer many other packages, e.g. _GAMA_ for multi-agent-simulation or _Obeo Designer Community_ for creating Sirius diagram editors.
[NOTE]
====
Several Eclipse packages can be installed side by side, even different releases of the same package. Multiple Eclipse installations can run at the same time, each on its own _workspace_ (see below).
====
.Plug-ins / Features
An installed Eclipse package consists of a runtime core and a bunch of additional plug-ins.
Technically, a plug-in is just a special kind of Java archive (JAR file) that uses and can be used by other plug-ins with regard to OSGi specifications.
Groups of plug-ins that belong together are called a _feature_.
Often, a user will add plug-ins or features to an Eclipse installation to add new capabilities.
E.g. writing this documentation within my Eclipse IDE is facilitated by the plug-in https://marketplace.eclipse.org/content/asciidoctor-editor[Asciidoctor Editor].
Plug-ins can easily be installed via main menu command `Help → Eclipse Marketplace...` or `Help → Install New Software...`.
Some plug-ins may be self-made like our plug-in `de.hftstuttgart.units` that enables Ecore to deal with quantities.
These may be provided via _Git_ or as download and have to be added to an Eclipse installation manually.
.Git
https://git-scm.com[Git] is the industry standard for collaborative work on, and versioning of, source code and other textual data.
Collaborative development of parameter catalogs benefits massively from using Git.
Git support is built into _Eclipse Modeling Tools_, the Eclipse package we will use.
However, if Eclipse needs to connect to a Git server that uses SSH protocol (not HTTPS with credentials), access configuration is more involved and may be dependent on your operating system.
Some users, anyway, prefer to use Git from the command line or with one of the client application listed https://git-scm.com/downloads/guis[here], e.g. https://tortoisegit.org[TortoiseGit] for Windows.
While it is required to get Git working at some point, we won't refer to it in this document and, for now, do not cover the installation of Git on your machine or configuration of Git in Eclipse.
.Workspaces
When you start a new Eclipse installation for the first time, you are asked to designate a new directory in your file system to store an _Eclipse workspace_.
Eclipse is always running with exact one workspace open.
As the name implies, a workspace stores everything needed in a given context of work, namely a set of related projects the user is working on as well as meta-data like preference settings, the current status of projects, to do lists, and more.
In case a user wants to work in different contexts, e.g. on different tasks, command `File -> Switch Workspace` allows to create additional workspaces and to switch between them.
[NOTE]
====
Any plug-in from the original Eclipse package or installed by the user later will be copied into the Eclipse installation directory, *not* in any workspace.
Configuration and current state of plug-ins, on the other hand, are stored in workspaces.
====
.Projects
An Eclipse project is a technical term for a directory that often contains:
* files of specific types for source code, scripts, XML files or other data
* build settings, configurations
* dependency definitions (remember the dependencies between plug-ins above?)
* other Eclipse projects.
`File -> New -> Project...` offers many different types of projects that the user can choose from, e.g. Java projects to create Java programs, Ecore modeling projects, or general projects, that simple hold some arbitrary files.footnote:[Projects possess one or more _natures_ used to define a project's principal type.]
[WARNING]
====
Files that do not belong to a project are invisible for Eclipse!
====
The projects belonging to a workspace can either be directly stored within the workspace as sub-directories (the default offered to the user when creating a new project), or linked from it, that is the workspace just holds a link to the project directory that lives somewhere in the file system outside of the workspace.
Linking allows to work with the same projects in different workspaces.
While it sometimes makes sense to share or exchange workspaces between users,footnote:[Or even work on the same workspace provided in the cloud, see https://www.eclipse.org/che/technology/[Eclipse Che].], I do not recommend this for now.
Projects, in contrast, are shared between users most of the time, usually via Git.
In general, I would suggest to store Eclipse projects outside workspaces at dedicated locations in the user's file system.
That way, we can follow the convention that local Git repositories should all be located under
`<userhome>/git`.
=== Setup Eclipse Modeling Tools
.Install Java
Eclipse runs on 64-bit versions of Windows, Linux, and macOS and requires an according Java Development Kit (JDK), version 11 or higher, to be installed on your machine.
Even if such JDK already exists, please download OpenJDK, version *15* or newer for your operating system from https://adoptopenjdk.net[AdoptOpenJDK].
footnote:[AdoptOpenJDK recently joined the Eclipse foundation and soon will change its name to _Adoptium_ for legal reasons.]
Choose `HotSpot` as Java Virtual Machine.
Installation process is straight forward, but you can also find links to exhaustive instructions for your operating system.
New Java versions appear every six months, so one could tend to stick with older version 11 that comes with long time support (LTE) until version 17 arrives in autumn 2021.
However, actual version 15 conforms to the latest security measures built into macOS Catalina, so it is a must if software we build here shall be deployed to these systems, too.
Note that different versions of Java coexist peacefully.
.Install Eclipse Modeling Tools
Now its time to download and install the correct Eclipse package _Eclipse Modeling Tools_, version 2020-09 or newer.footnote:[Please stay away from version 2020-03 and 2020-06 of Eclipse Modeling Tools, since these came with a bug preventing the user from editing data in table cells within the generated UI.]
Please go to https://www.eclipse.org/downloads/packages[Eclipse download page for packages].
On this page you may see _"Try the Eclipse Installer"_ or similar.
Do *not* follow this advice, since we want more control over what versions of Java and Eclipse shall be installed.
Instead, look for package _Eclipse Modeling Tools_ and follow the link for your operating system on the right:
.Download links for Eclipse Modeling Tools package
image::EclipseDownload.gif[EclipseDownload, role="thumb"]
Finally, you can click on `Download` and wait for the 400 something MB package to arrive.
[NOTE]
====
Depending on the operating system, several security dialogs have to be acknowledged during installation and first launch of Eclipse.
====
The downloaded installation file contains the application simply named `Eclipse` ready to be copied into `Applications` on macOS or be installed in `Programs` on Windows.
Since later you may add other Eclipse packages -- or different versions of the same package -- I suggest to rename the application more significantly to `EclipseModeling2009` or similar.
After installation has finished launch Eclipse for the first time and you will see a dialog for choosing a new empty directory as its workspace.
.Initial Dialog to Choose a Workspace Directory
image::SelectWorkspaceDirectory.gif[SelectWorkspaceDirectory, 500, role="thumb"]
Again, more workspaces might come into existence later, so replace the proposed generic directory path and name with a more specific one, e.g.`EclipseModelingWS`.
The Eclipse main window appears with a Welcome Screen open.
It contains links to exhaustive documentation on concept, features and usage of Eclipse that might be of interest later, especially:
* Overview
** Workbench basics
*** Concepts: features, resources, perspectives, views, editors
*** Opening perspectives and views
*** Installing new software manually
** Team support with Git
* Learn how to use the Ecore diagram editor
* Launch the Eclipse Marketplace
For now, you can dismiss the welcome screen. It can be opened anytime by executing `Help -> Welcome`
=== Modeling Parameter Catalogs for Simulation with Ecore
Now you should see the initial layout of Eclipse with _Model Explorer_ and _Outline_ on the left and a big empty editing area with _Properties_ view below to the right.
Since we will use Ecore diagrams for data modeling, create your first Ecore modeling project now:
. Execute `File -> New -> Ecore Modeling Project` from main menu -- not `Modeling Project`!
. Name it `demo.catalog` and click `Next >`
. Uncheck `Use Default Location` so that the new project is *not* stored in workspace, but a different directory you create/choose, then click `Next >`
. Provide `democatalog` as main Java package name and click `Finish`.
Eclipse should look like below with an new empty graphical Ecore diagram editor opened.
The diagram is automatically named `democatalog` after the package name for the Java classes that will be generated from it (provided above).
The _Model Explorer_ shows the contents of the new Ecore modeling project.
.New Ecore Modeling Project
image::DemoCatalogEmpty.png[DemoCatalogEmpty, role="thumb"]
To get your feet wet, do this:
. Drag a _Class_ from the palette on the right onto the editor's canvas: it will materialize as a rectangle labeled `NewEClass1`.
. The class symbol should be selected initially, so you can see its attributes in the _Properties_ view.
. In there replace `NewEClass1` by `EnergyComponentsCatalog` to rename the class.
. Click anywhere on the canvas and notice that the class symbol is deselected and the toolbar at the top adapts accordingly.
. In the toolbar change `100%` to `75%` to scale diagram.
. Execute `File -> Save` to save model and diagram on disk.
. Close diagram editor `democatalog` by closing its tab.
. Reopen saved diagram by double click on entry `democatalog` in _Model Explorer_.
Technically, everything is in place now to begin modeling the data that the projected catalog shall contain.
Except ... understanding the basics of object-oriented modeling would be helpful.
This is why developers should support domain experts at this stage.
.Model Data with Class Diagrams
Ecore diagrams are simplified UML class diagrams.
Here some resources on what this is all about:
* http://www.cs.toronto.edu/~sme/CSC340F/slides/11-objects.pdf[Toronto Lecture on Object Oriented Modeling]
* http://agilemodeling.com/artifacts/classDiagram.htm[UML 2 Class Diagrams: An Agile Introduction]
* https://www.amazon.de/UML-Classroom-Einführung-objektorientierte-Modellierung-ebook/dp/B00AIBE1QA/ref=sr_1_2?__mk_de_DE=ÅMÅŽÕÑ&dchild=1&keywords=UML&qid=1585854599&sr=8-2[UML @ Classroom: Eine Einführung in die objektorientierte Modellierung (German Book)]
[TIP]
====
Beginners are strongly encouraged to read the first two resources.
The first one contains a gentle introduction, especially suited for domain experts.
The second one can also serve as reference.
====
We will touch central object-oriented concepts _Class_, _Object_, _Attribute_, _Association_, _Composition_, and _Multiplicity_ in an example below, but work through above sources to get a deeper understanding and to enhance your modeling skills.
Note that above sources differentiate between _conceptual_ and _detailed_ models.
All in all we go for detailed models, since only these contain enough information to generate code.
Having said this, it is usually a good idea to have two or three conceptual iterations at a white board to agree on the broad approach before going too much into detail.
But even if one starts with Ecore models right away, these also can be adapted any time to follow a new train of thought.
See here the essential and typical structure of a parameter catalog in a class diagram.
Instead of artificial example classes like _Foo_ and _Bar_ it shows classes from an existing catalog, albeit in very condensed form.
.Principle Structure of a Parameter Catalog
[plantuml, role="thumb"]
----
together {
class SolarPanel
class Inverter
}
class EnergyComponentsCatalog {
author: String
}
abstract class EnergyComponent {
modelName: String
revisionYear: int
}
abstract class ChemicalEnergyDevice {
installedThermalPower: double
}
class Boiler {
type : BoilerType
}
class CombinedHeatPower {
thermalEfficiency : double
electricalEfficiency : double
}
class Manufacturer {
name : String
}
enum BoilerType {
LowTemperature
Condensing
}
class SolarPanel {
nominalPower : double
mppVoltage : double
mppCurrent : double
}
class Inverter {
nominalPower : double
maxDCVoltage : double
maxDCCurrent : double
}
BoilerType -[hidden]- Boiler
SolarPanel --|> EnergyComponent
Inverter --|> EnergyComponent
ChemicalEnergyDevice --|> EnergyComponent
Boiler --|> ChemicalEnergyDevice
CombinedHeatPower --|> ChemicalEnergyDevice
EnergyComponentsCatalog *-- "0..*" Inverter: inverters
EnergyComponentsCatalog *-- "0..*" SolarPanel: solarPanels
EnergyComponentsCatalog *-- "0..*" Boiler: boilers
EnergyComponentsCatalog *-- "0..*" CombinedHeatPower: chps
EnergyComponentsCatalog *-- "0..*" Manufacturer: manufacturers
EnergyComponent -up-> "1..1" Manufacturer: producedBy
----
The diagram models four types of technical components whose data shall be stored in the catalog, e.g. for parameterization of simulation models later: _Boiler_, _CombinedHeatPower_, _SolarPanel_, and _Inverter_.
The catalog itself is represented by class _EnergyComponentsCatalog_.
Unlike dozens, hundreds, or even thousands of objects to be cataloged -- Boilers, Inverters etc. -- there will be just exactly *one* catalog object in the data representing the catalog itself.
Its "singularity" is not visible in the class diagram, but an _Ecore_ convention requires that all objects must form a composition hierarchy with only one root object.
.Composition
If, in the domain, one object is composed of others, this is expressed by a special kind of association called _composition_.
Compositions are depicted as a link with a diamond shape attached to the containing object. In the _Boiler_ case said link translates to: The _EnergyComponentsCatalog_ contains -- or is composed of -- zero or more (`0..*`) boiler objects stored in a list named `boilers`.
[IMPORTANT]
====
Note that class names -- despite the fact that they model a set of similar objects -- are always written in _singular_! They are written in https://en.wikipedia.org/wiki/Camel_case[Camel case notation] starting with an upper case letter. Associations and attributes are written the same way, but starting with a lower case letter. Names for list-like associations and attributes usually are written in plural form.
====
.Inheritance
Besides composition of *objects*, the model above shows another, completely different, kind of hierarchy: the inheritance hierarchy between *classes*.
Whenever classes of objects share the same attributes or associations, we don't like to repeat ourselves by adding that attribute or relation to all classes again and again.
Instead, we add a _super class_ to define common attributes and associations and connect it to _sub classes_ that will automatically _inherit_ all the features of their super class.
In our example above, common to all four energy components are attributes `modelName` and `revisionYear`, thus these are modeled by class `EnergyComponent` that is directly or indirectly a super class of _Boiler_, _CombinedHeatPower_, _SolarPanel_, and _Inverter_.
Similar, _Boiler_ and _CombinedHeatPower_ share attribute `installedThermalPower` factored out by class _ChemicalEnergyDevice_.
.Associations
You probably noticed a fifth type of objects contained in the catalog, namely `Manufacturer` objects stored in list `manufactureres`.
How come? Ok, here is the story:
.Domain Expert Meets Developer
****
_Exp_: "`I'd like to store a component's manufacturer. Shall I add a String attribute `manufacturerName` to all classes like _Boiler_, _Inverter_ and so on to store the manufacturer's name?`"
_Dev_ shudders: "`Well, what do you mean by "... and so on"?`"
_Exp_: "`Basically, I mean all energy components.`"
_Dev_: "`Fine. We already have a class representing all those energy components, brilliantly named _EnergyComponent_. Thus, we can define `manfacturerName` there, following one of Developer's holy principles: "_DRY_ -- Don't repeat yourself!"
By the way: Is the name all you want to know about manufacturers?`"
_Exp_: "`Mhm, maybe we need to know if they are still in business ...`"
_Dev_: "`... or even since when they were out of business, if at all ...`"
_Exp_: "`... and the country or region they are active.`"
_Dev_: "`Ok, so it's not just the name -- we need a class `Manufacturer` to model all these information.`"
_Exp_ sighs.
_Dev_: "`Come on, its not that hard to add a class to our data model, isn't it?`"
_Exp_: "`Ok, but how can we express what components a manufacturer produces?`"
_Dev_: "`Wasn't it the other way around? I thought, you just wanted to know the manufacturer of a component?`"
_Exp_: "`What is the difference?`"
_Dev_: "`In data modeling, it is the difference between a uni-directional and a bi-directional association.`"
_Exp_: "`...?`"
_Dev_: "`Let's put it that way: The difference between a link with an arrow on one side or on both sides.`"
_Exp_: "`Ok. We don't need a list of components per manufacturer, but simply a reference from the component to its manufacturer.`"
_Dev_: "`Fine, then in Ecore please create a simple reference from class `EnergyComponent` to class `Manufacturer`, maybe named `producedBy`.`"
_Exp_: "`I will try this and get back to you.`"
_Dev_: "`Fine ... good meeting.`"
****
Observe in our data model, reference `producedBy` points _from_ `EnergyComponent` _to_ `Manufacturer` making it uni-directional reference.
One can simply query the manufacturer of a product, but not so the other way around.
With a bi-directional reference both queries would be available.
Observe also the annotations `0..*` and `1..1` near class `Manufacturer`.
These are _multiplicities_ of associations: An `EnergyComponentsCatalog` contains zero, one, or many objects of class `Manufacturer` and an `EnergyComponent` must reference exactly one manufacturer -- not less, not more.
[.float-group]
--
.Ecore Relations
image::EcoreRelations.gif[EcoreRelations, 200, float="right", role="thumb"]
To recapitulate: Our example parameter catalog already exhibits all four types of relations provided by Ecore.
You find these in the Ecore editor's palette shown here.
To create a relation between a sub class and a super class use tool `SuperType`.
Use the other tools to create an association between classes, may it be a simple (uni-directional) reference, a bi-directional reference, or a composition.
--
.Attributes and Enumerations
Obviously, attributes are central in data modeling.
Create one by dragging it from the palette onto our one and only class so far: `EnergyComponentsCatalog`.
The class symbol will turn red to indicate an error.
Hover with the mouse pointer over the new attribute and a tooltip with a more or less helpful error message will appear.
Current error is caused by that no data type was set for the new attribute.
Data types for attributes can be integer or floating point numbers, strings, dates, booleans, and more.
To get rid of the error:
. If not already selected, select new attribute by clicking at it in the editor.
. In view _Properties_ find `EType` and click button `...` to see a quite long list of available data types.
. Choose `EString [java.lang:String]` from the list and the error is gone.
[.float-group]
--
.Class with Attribute
image::EcoreClassWithAttribute.png[EcoreClassWithAttribute, 200, float="right", role="thumb"]
Change the attribute's name to `author` and the class should look like shown here.
Most data types to choose from begin with letter *E* like in **E**core.
These are just Ecore enabled variants of the respective Java types, thus, choose EInt for an int, EFloat for a 32 bit floating point number, EDouble for a 64 bit one, and so on.
Ecore allows to introduce new data types.
We employ this feature later to enable data models with physical units and quantities.
--
There exists one other means to define the values an attribute can take, namely enumerations of distinct literals. Take _Monday_, _Tuesday_, _Wednesday_, ... as a typical example for representing weekdays.
In our example data model you'll find one _Enumeration_ named `BoilerType` with values `LowTemperature` and `Condensing`.
.Homework
The next section deals with generation of Java code from data models. To have more to play with, please implement our example model in Ecore now.
[.float-group]
--
.Abstract Class
image::EcoreClassifier.png[EcoreClassifier, 200, float="right", role="thumb"]
To do this, there is one more thing to know about classes: the difference between ordinary classes and abstract classes.
'Ordinary class' doesn't sound nice, therefore, classes that are not abstract are called _concrete_ classes.
Our example diagram depicts abstract classes with letter *A* while concrete classes are labeled with *C*. You add abstract classes to a model with a special palette tool shown here.
The thing is: Objects can be created for concrete classes only!
In our example, it makes no sense to create an object from class _EnergyComponent_, because there is not such a thing like an energy component _per se_.
Therefore, this class is _abstract_.
It is true that an inverter _is_ an energy component, thus inheriting all its features, but it was _created_ as _Inverter_, not as _EnergyComponent_.
Super classes will be abstract most of the time.
So my advice is: Model a super class as abstract class unless you convince yourself that there exist real objects in the domain that belong to the super class but, at the same time, do not belong to any of its sub classes.
In the Ecore editor properties view, you can specify if a class is abstract or not, simply by toggling check box `Abstract`.
--
Two more tips and you are ready to rock and roll! -- At least with your homework.
[TIP]
====
An exhaustive user manual for Ecore diagram editor is available. Execute `Help -> Welcome` and follow link `Learn how to use the diagram editor`.
====
[TIP]
====
If Ecore models get bigger, you may find it more convenient to work with a form based UI instead of, or in addition to, the diagram editor.
Open this kind of editor via command `Open With -> Ecore Editor` from the context menu over entry `democatalog.ecore` in the _Model Explorer_ view.
Note that Eclipse synchronizes different editors of the same content automatically.
====
=== Generation of Java Code from Data Model
By now, your Ecore model should look like this:
[[fig-example-model]]
.Example Model (Homework)
image::Homework.gif[Homework, role="thumb"]
Let us bring the model to life, that is, generate code from it that creates, reads, updates, and deletes concrete data objects of modeled classes in computers.
I would like to tell you that this is done with just one click but, actually, you need two or three:
. Make sure all files are saved (`File -> Save All`)
. Execute `Generate -> Model Code` from context menu over `democatalog.ecore`
. Execute `Generate -> Edit Code` from context menu over `democatalog.ecore`
[WARNING]
====
Please do *not* execute `Generate -> All` or `Generate -> Editor Code`.
image::GenerateMenu.png[GeneratedClasses, 260, role="thumb"]
This would create code for a simple user interface, but we use more advanced EMF Forms for that later.
If, by mistake, project `demo.catalog.editor` was created, just delete it from _Model Explorer_ and do not forget to check `Delete project contents on disk` in confirmation dialog.
====
[.float-group]
--
.Generated Classes
image::GeneratedClasses.png[GeneratedClasses, 260, float="right", role="thumb"]
`Generate -> Model Code` creates classes that represent the modeled data in code. These classes are located in three packages under directory `src-gen` in `demo.catalog`.
`Generate -> Edit Code` creates a whole new Eclipse project named `demo.catalog.edit`, again with generated classes under directory `src-gen`.
You may have a look at some Java classes for curiosity by double clicking at them in _Model Explorer_. There is no point in trying to understand the code in detail, but observe token `@generated` present in the comments of all classes, fields and methods. Classes, fields and methods marked with this token are (re)generated whenever above commands are executed.
Sometimes it maybe required to manually adapt generated code -- after all our concern is "low code", not "no code" development. In that case, we will replace `@generated` by `@generated NOT` to prevent code regeneration.
After code generation, you may have noticed some warnings showed up in view _Problems_.
.Warnings
image::Warnings.gif[Warnings, 500, role="thumb"]
In general, it is highly recommended to resolve warnings, and errors of course, but we will make an exception from the rule, since the warnings are uncritical and would reappear each time code is regenerated.
--
=== Generation and Tweaking of User Interface
In this section you will learn how to generate and tweak a CRUD user interface based on Ecore data model and Java classes created for our demo parameters catalog above. Topics described here are discussed in more detail in tutorial https://eclipsesource.com/blogs/tutorials/getting-started-with-EMF-Forms/[Getting started with EMF Forms].
To find out what user interface controls and layouts are provided by this framework have a look at https://eclipsesource.com/blogs/tutorials/emf-forms-view-model-elements/[EMF Forms – View Model Elements]. _EMF Forms_ is already part of package _Eclipse Modeling Tools_, so we can create a third Eclipse project/plugin that implements a user interface for editing catalog data without further ado:
. From context menu over `democatalog.ecore` execute `EMF Forms -> Create View Model Project`
. Leave project name `demo.catalog.viewmodel` as is but uncheck `Use default location` -- as we always do -- and browse to the directory containing `demo.catalog`
. Click `Next >` and select `EnergyComponentsCatalog` as data element we want to create a user interface for
. Leave `Fill view model with default layout` checked and click `Finish`.
According to these inputs a new project is created with file `EnergyComponentsCatalog.view` under directory `view models`.
This file opens automatically in a special _View Editor_.
.New View Model
image::ViewModel.png[ViewModel1, role="thumb"]
Like the *data* of our catalog are modeled as Ecore file using a dedicated graphical editor, so will our catalog’s *user interface* be modeled in `.view` files, again using a special editor.
Since we opted for `Fill view model with default layout` the catalog's UI is filled initially with default controls for all data items assigned to Ecore type `EnergyComponentsCatalog` like a string control for `author` or list controls for `boilers`, `chps`, and so on.
See red arrow in the above screen-shot?
It points to a button that opens a functional preview of the modeled user interface.
.User Interface Preview
image::ViewEditorPreview.png[ViewModel1, 500, role="thumb"]
[TIP]
====
Double click on tab _EMF Forms Preview_ to enlarge view for better handling -- double click again to get back.
Enable auto refresh mode image:ViewModelAutomaticRefresh.gif[ViewModelAutomaticRefresh, 40] to let each change in the view model instantly be reflected in the preview.
Given your screen is big enough, you may want to dock-out the preview by dragging tab _EMF Forms Preview_ out of Eclipse's main window.
Seeing editor and preview side by side is a great way to explore the possibilities of view models.
====
Red input field and exclamation mark in the preview signal missing or inconsistent data.
Ecore data model specifies attribute `author` with a lower bound of one, meaning it is a mandatory attribute.
As soon as an author's name is provided, the error indication disappears.
This is what _functional_ preview means.
You can even create new boilers or other objects in lists provided, with all forms created "automagically" with respect to our underlying Ecore data model.
Of course, such automatic approach has its limits.
In our case, to have a long list of lists is not very user-friendly, because one has to scroll up and down to find a specific list.
Also, no specific object data are shown in the list and data can only be edited in a pop-up form (no inline editing).
How should a better UI look and feel like?
If there are many lists (types) of entities -- the normal case for parameter catalogs -- users should select what list they want to work with by selecting it from a list or tree view that is always visible, the _master view_.
Once a type is selected in the master view, a table with all objects of this list/type shall appear sidelong in a _detail view_, ready for editing.
In _EMF Forms_ master-detail-views can be modeled either with _Categorization_ or _Tree Master Detail_ UI components.
The latter not only allows to edit information displayed in the detail view, but also the tree of elements in the master view.
Opposed to that, a _Categorization_ presents a fixed hierarchy of elements to choose from.
This is exactly what we need as there are only a fixed number of types of objects to be edited in a parameters catalog.
==== Adding Tables to the UI
[.float-group]
--
.Delete default list controls
image::ViewModelDeleteControls.gif[ViewModelDeleteControls, 300, float="right", role="thumb"]
But first, we replace the default controls for lists of boilers, chps, and so on by tables. As shown here, select all list controls in the view model and execute `Delete` from context menu. Refresh _View Editor Preview_ to verify that only field `Author*` is left.
--
[.float-group]
--
.Create Table Control
image::ViewModelCreateTable.gif[ViewModelCreateTable, 300, float="right", role="thumb"]
Next, create a table that shall display all boilers in a catalog:
Select `EnergyComponentsCatalog`, activate context menu and choose `TableControl` from the list of available UI elements.
(EnergyComponentsCatalog represents the root view of the UI and, as such, accepts quite a lot of different UI components as child components.)
Entry `TableControl` was inserted into the list of interface elements below `Control author`.
Checking updated preview reveals no table but a message basically saying that a reference to the domain model is missing, in other words: _EMF Forms_ does not know yet what data to present in table.
Click on entry `TableControl` to see its details.
A red exclamation mark indicates the missing `Domain Model Reference*`.
Click on image:ButtonLinkPlus.gif[ButtonLinkPlus, 40] and be ready to chase a sequence of dialogs:
--
. Click on another image:ButtonLinkPlus.gif[ButtonLinkPlus, 40] in dialog `Configure TableDomainModelReference`
. In wizard `New Reference Element` select `model -> FeaturePathDomainModelReference` and click `Next >`
. Click `Link Domain Model EFeature` and in appearing pop-up list choose reference to list of objects you want to edit in the table, e.g. `boilers`; confirm with `OK` safely ignoring warning about missing `PropertyDescriptor`.
. `Finish` wizard `New Reference Element`
. `Finish` dialog `Configure TableDomainModelReference`.
This was some work, but as reward we get a fully specified table control in _View Editor_ that "translates" into a preview where we can create, read, update, and delete boilers.
.Table for Boilers
image::ViewModelWithTable.gif[ViewModelWithTable.gif, role="thumb"]
Moreover, clicking at a table header sorts all objects in it (rows) according to the values in this column.
Column widths can adapted, too.
[.float-group]
--
.Modify Table Control
image::ViewModelTweakTable.gif[ViewModelTweakTable, 300, float="right", role="thumb"]
Table UIs can be tweaked in many ways, e.g. selection and sequence of columns can be declared via list `Column Domain Model References`. To fill this list with defaults, execute `Generate Columns` from table control's context menu. Reorder them as you like or delete columns that are not important to the user.
Notice here an important overall feature of _EMF Forms_: If something is left unspecified, be it the view model for an Ecore object type or the specification of table columns, _EMF Forms_ will always find a default solution! Applied to columns specification this means we get default columns automatically back in the moment the last column is removed from list `Column Domain Model References`.
If explicit column specifications are present further configurations can be added to a table control from its context menu, e.g. initial column widths or read-only status of columns. See https://eclipsesource.com/de/blogs/2018/01/31/emf-forms-1-15-0-feature-enhanced-table-renderer/[here] for details.
--
By default only attributes are displayed and directly editable in tables while references to other objects -- in our case the reference to a manufacturer -- are not.
[.float-group]
--
.Default Panel for Boilers
image::ViewModelWithPanel.gif[ViewModelWithPanel, 300, float="right", role="thumb"]
To get the default (_sic!_) editing panel for an selected table row, in _View Editor_ just set `Detail Editing*` from `None` to `WithPanel`, *press _Tab_*, and save. For boilers, _EMF Forms_ will create the editing panel shown here. Regardless wether users edit data in the panel or directly in the table -- both will stay in sync any time.
--
[WARNING]
====
_View editor_ exhibits an irritating behavior: With preview auto-refresh turned on, any change in the details view is reflected instantly in the preview, even without saving the form or leaving the edited field.
On the other hand, *saving* an updated view editor only takes into account edited fields after they have lost focus, e.g. by pressing _Tab_ key or clicking with the mouse into another field.
So, saving a form before the focus has shifted from the last edited field won't honor this edit, that is you won't necessarily get what you see.
====
One last thing: Enter `boilers` as name for the table control so we can distinguish it from the other four table controls to come.
Yes! ... Please repeat above procedure to create table controls for chps, solar panels, inverters and manufacturers, too. I did this in about 3 minutes. ;-)
==== Master-Detail View with Categories
In last section we improved our catalog's UI by replacing simple object lists by tables that can be sorted, customized and edited inline as well as in an associated panel.
Alas, instead a list of lists we have got an even bigger list of tables.
High time to introduce a master-detail view that presents categories of object types in a master view and, after one is selected, the according object table as detail.
[.float-group]
--
.Category Tree
image::ViewModelCatgorization1.gif[ViewModelCatgorization1, 180, float="right", role="thumb"]
Add a _Categorization_ view to the list of UI elements in _View Editor_ by selecting `EnergyComponentsCatalog` and choose `Categorization` from its contect menu.
Now add two `Composite Category` elements and one `Leaf Category` to `Categorization` from according context menu. This gives us three top level entries in the hierarchy.
In the same way add two `Leaf Category` elements to each `Composite Category` resulting in the hierarchy depicted here.
--
[.float-group]
--
.Completed View Model
image::ViewModelCatgorization2.gif[ViewModelCatgorization2, 260, float="right", role="thumb"]
This screen shot shows the view model of our UI when finished. To get there:
. Select UI element `Categorization` and rename it to `Categories`
. Rename composite and leaf categories as depicted here
. Drag all table controls one by one into the suited leaf category
. Confirm master-detail view works as expected in the preview.
--
[IMPORTANT]
====
The UI hierarchy to access tables for entity types is independent, and usually will differ, from aggregation and inheritance hierarchies present in Ecore data model (compare fig. <<fig-example-model, Example Model>>).
====
Note that _EMF Forms Preview_ provides these buttons image:ViewModelPersistence.gif[PreviewPersistanceButtons, 68] to clear, load and store edited data.
In fact, this feature gives us a fully functional prototype.
At least during refinement of model and UI, data sets can be created, edited, and tested for usability without the need to built a full blown, deployable application -- see parts _Accessing and Using Parameter Catalogs_ and _Build (Parameter Catalog) Applications with Eclipse Tycho_ below.
Be aware that in some cases the view model must adapt to changes in the data model, e.g. a new leaf category and table component has to be created for a new catalog object type.
Other changes are automatically reflected in the generated UI, at least for default forms and other UI elements.
To our convenience, view model specifications incompatible with data model are indicated by error badges in the _View Editor_.
Changes in data model also can make existing XML data incompatible. There are tools for data migration, but for now, recreation of test data or manual editing of XML file is the way to go.
==== Summary
What have we achieved so far?
We created a graphical Ecore data model with a catalog class and five classes/types of objects therein.
Classes have been defined by name, attributes, and relations between, often with cardinalities.
Whenever classes shared some attributes or references we factored these out into super classes.
An enumeration introduced a new attribute type from a set of named values.
From this data model, we issued commands to create matching Java code for representing the data in memory as well as to store and retrieve them on and from disk. Methods to create, read, update and delete data objects (CRUD) were generated, too.
Lastly, we thought about a good user interface for this data and used _EMF Forms_ to model and prototype it.
=== Bonus: Solutions for Specific Modeling Problems
==== Add Units to the Mix
*TBD*
As mentioned earlier, parameter catalogs for simulations should be able to represent quantities, not just bare integer and real numbers.
using Indrya, the reference implementation for Units of Measurement in Java (JSR 385)
To this end, the author has created two Eclipse plug-in projects providing this feature to be used by Ecore and EMF Forms.
Third-party libraries like Indrya, usually, are not distributed as plug-ins, but _Tycho_ can wrap them automatically as OSGi plug-ins that can added directly to our application.
Another plug-in, created by the author connects the Ecore and Indrya. We will compile it from source code, simply by importing the projects.
. Copy to file system ...
. Import project but *not* copying it in the workspace (just linking)
==== Represent Functions in a Parameter Catalog
*TBD*
for creating custom UI labels:
* `ExponentialFunctionItemProvider.java`
* `LinearFunctionItemProvider.java`
* `TableFunctionItemProvider.java`
Custom code marked with `@generated NOT` in `de.hftstuttgart.energycomponents.provider` in project `de.hftstuttgart.energycomponents.edit`
==== How to Model Derived References and Attributes
*TBD*
We haven't used derived references or attributes by now. But if one has to implement some by providing a getter, it is necessary to return an unmodifiable list like BasicEList.UnmodifiableEList or EcoreUtil.unmodifiableList(...) instead of EList as described here: https://www.ntnu.no/wiki/plugins/servlet/mobile?contentId=112269388#content/view/112269388 .
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