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Graphical Modeling Framework/Tutorial/Part 1

< Graphical Modeling Framework‎ | Tutorial
Revision as of 12:17, 6 March 2006 by Rgronback (Talk | contribs) (Running the Diagram)

Warning: this tutorial is undergoing an update to 1.0M5 of GMF

This tutorial will introduce the Graphical Modeling Framework (GMF), an Eclipse Technology subproject which aims to provide a generative bridge between the Eclipse Modeling Framework (EMF) and Graphical Editing Framework (GEF). In this tutorial, a mindmap application will be developed, as described here. This tutorial describes the functionality provided by GMF in its current state, using this build (1.0M5). It is expected that this tutorial will evolve with GMF to introduce new functionality as it is developed.

Overview of GMF

The use of both EMF and GEF for building Eclipse-based functionality is quite common. Many references below provide information on how to utilize these frameworks together, some of which inspired the GMF project itself. Before diving into a new GMF project, let's explore a little of how GMF approaches the task of utilizing EMF and GEF in a generative manner. Another article focusing on the runtime portion of GMF is found here.

The GMF project has adopted the term 'toolsmith' to refer to developers that use GMF to build plug-ins, while 'user' is typically refered to those who utilize said plug-ins, and who may also be developers. From a usability perspective, the number and types of 'models' utilized by GMF internally should be hidden to the greatest extent possible. However, it is likely that most toolsmiths are interested in knowing what is going on under the covers, so a description of each model is presented in this tutorial.

GMF Overview

This is a diagram that illustrates the main components and models used during GMF-based development. Core to GMF is the concept of a graphical definition model. This model contains information related to the graphical elements that will appear in a GEF-based runtime, but have no direct connection to the domain models for which they will provide representation and editing. An optional tooling definition model is used to design the palette and other periphery (overview, zoom, etc.).

It is expected that a graphical or tooling definition may work equally well for several domains. For example, the UML class diagram has many counterparts, all of which are strikingly similar in their basic appearance and structure. A goal of GMF is to allow the graphical definition to be reused for several domains. This is achieved by using a separate mapping model to link the graphical and tooling definitions to the selected domain model(s).

Once the appropriate mappings are defined, GMF provides a generator model to allow implementation details to be defined for the generation phase. The production of an editor plug-in based on the generator model will target a final model; that is, the diagram runtime (or "notation") model. The runtime will bridge the notation and domain model(s) when a user is working with a diagram, and also provides for the persistence and synchronization of both. An important aspect of this runtime is that it provides a services-based approach to EMF and GEF functionality and is able to be leveraged by non-generated applications.

With the basics of GMF covered, let's now walk through the process of using GMF in the development of a graphical editing surface for a particular domain. First, you will need to install GMF and its dependencies.

Setup

This version of the tutorial was written using this build of GMF (1.0M5). Note that the prerequisites are listed on the build page, which must be installed prior to installing GMF, either from the download page, or from the update manager site. The TaiPan example referenced below is maintained in CVS and should remain functional with the latest builds of GMF, even if the tutorial is not quite up-to-date.

Quick Start

Checkout.png

If you're anxious to see GMF in action, check out the Taipan example projects into your workspace from CVS by switching to the CVS Repository Exploring perspective and adding a repository location as shown in the image to the right. Otherwise, you can skip to the next section.

Navigate to /HEAD/org.eclipse.gmf/examples and select the three org.eclipse.gmf.examples.taipan.* modules. Right-click and select Check Out. If you are not using the latest build and prerequisites of GMF, you can always check out the version of the Taipan by date to correspond with the version you're using. The important point is that you'll need to work with synchronized versions of the GMF SDK and the Taipan example. To do this, after checkout you can right-click on the projects and selecting 'Team | Switch to Another Branch or Version...' and then choose 'Select the tag from the following list' and use the 'Add Date...' button at the bottom to enter the date of the GMF 1.0M5 release (03 Mar 2006). Press Finish and you're set.

Switch to the Plug-in Development perspective and open the models folder within the org.eclipse.gmf.examples.taipan project. Explore each of the models found here, particularly the taipan.gmfgraph and taipan.gmfmap models and their element properties.

We will look at each of the models in turn during the tutorial, but just to validate your configuration, you should be able to run this sample in a runtime workspace (simply accept the defaults for a new 'Eclipse Application' run configuration). In the runtime workspace, create an empty project and a new 'TaiPan Diagram' found in the Examples folder of the New dialog. Name it whatever you wish and click Finish. The generated diagram editor should open for you to explore. Some things to note in particular are:

  • tool palette and overview
  • layout and selection tools
  • diagram image export (svg, bmp, jpeg, gif)
  • tabbed properties view
  • font and color options for selected element
  • link routing and style options
  • pop-up bars and connection handles
  • notes and geometric shapes
  • animated zoom and layout
  • diagram printing
Taipan diagram.png

This concludes the quick start portion of this tutorial. What follows next is a more detailed look at each of the models shown above during the creation of a mindmap modeling surface.

A New Project

As described here, one of the usage scenarios for GMF includes producing a graphical surface for a mindmap application, to be complemented with an alternative view of its temporal information (likely a Gantt chart). This section of the tutorial will demonstrate GMF's capabilities toward this end, and will continue to evolve as the project matures. If you'd prefer to follow along using a set of projects representing the complete solution to this tutorial, you can find a zip of them here.

Cheatsheet project.png

New to GMF is a Tutorial Cheat Sheet found under 'Help | Cheat Sheets...' If you open this cheat sheet and follow through each step, you can accomplish most of this first tutorial segment, while taking advantage of some actions that will launch and pre-populate wizards to get you started. Try this now to create your new project.

Alternatively, you can begin by creating an "New GMF Project" found under 'Graphical Modeling Framework' in the New dialog (Ctrl+N). Name the project 'org.eclipse.gmf.examples.mindmap' and create a new folder named 'model' in its root.


Domain Model Definition

Although it may seem necessary to begin with the domain model, it is not in the case with GMF, as the diagram definition is maintained separate from the domain. However, we will begin with the domain in the tutorial as it is likely familiar to most, and will allow us to jumpstart our diagram definition from the domain model using a wizard in the next section.

A basic domain model for our mindmap is found here. Copy this file into your 'model' folder and feel free to examine the model, if you wish. GMF provides a (bootstrapped) graphical editor to complement the standard EMF generated editors. In order to use the GMF Ecore editor, you will need to install the GMF Examples feature. To render the mindmap.ecore (or any *.ecore model) with the editor, simply right-click the file and select 'Initialize ecore_diagram diagram file' from the menu. The next step is to layout the diagram using the 'Arrange All' action.

Mindmap domain model

To continue, create a new mindmap.genmodel from the mindmap.ecore file using the New > Eclipse Modeling Framework > EMF Model wizard. You may wish to change the 'Base Package' property for the genmodel's 'Mindmap' package to org.eclipse.gmf.examples to have your generated packaging match the project name. These steps are also covered in the next step of the cheat sheet.

Tip : Be sure to give your genmodel file the same name as your domain model (i.e. both mindmap.*), as GMF currently expects this naming convention to identify the genmodel for the mapped domain model.

Generate the model and edit code using the right-click menu available from the root of the generator model. There is no need to create an editor or tests, but you are welcome to do so if you'd like. Now, we're ready to begin creating the graphical and mapping definitions for our mindmap application.

Graphical Definition

Graphical Definition Model, view in actual size.

A graphical definition model is used to define the figures, nodes, links, etc. that you will display on your diagram. The model you will work with to do this is seen at the right.

Continuing on with the next step in the cheat sheet, we will create a new graphical definition model. The cheat sheet will launch the GMFGraph Model wizard, which is found in the Graphical Modeling Framework folder of the New (Ctrl + N) dialog. Select the 'model' folder under your org.eclipse.gmf.examples.mindmap project for the mindmap.gmfgraph model, and on the next page of the wizard use 'Browse' to locate your mindmap.ecore file.

On the last page of the wizard, select a minimal set of element, link, and label options for our Topic class as shown in the image. Later on, feel free to experiment with this wizard and observe its output. For now, we're just interested in getting a minimal set of models to get started. Click 'Finish' to complete.

If you examine the model, you will find a Canvas at the root with a Figure gallery containing basic Rectangle, Label, and Polyline Connection elements. These are used by corresponding Node, Diagram Label, and Connection elements to represent our Topics from the domain model. We can leave the defaults as-is for now and continue with our tooling definition in the next step of the cheat sheet.

Cheatsheet graph.png

Tip : There are several figure galleries intended for reuse and included with GMF. You can load these into your *.gmfgraph model (or *.gmfmap model) by using "Load Resource..." and entering platform:/plugin/org.eclipse.gmf.graphdef/models/basic.gmfgraph for the Resource URI. Others available include classDiagram.gmfgraph and stateDiagram.gmfgraph.

Tooling Definition

Tooling Definition Model, view in actual size.

As mentioned above, the tooling definition model is used to specify the palette, creation tools, actions, etc. for your graphical elements. To the right is a diagram of the model.

The cheat sheet will guide you through a very similar process for getting started with our Tooling definition model. In fact, the two steps are virtually identical, as the mindmap domain model is loaded and examined for possible tooling needs. We will simply select the same options we did for the graphical definition and begin with a very simple palette for our Topic elements.
Cheatsheet tool.png

Looking at the model provided for us, we see there is a top-level 'Tool Registry' element, under which we find a Palette. The palette contains a Tool Group with Creation Tool elements for both Topic nodes and links for subtopic elements that were identified by the wizard. We will reorganize these and modify them a bit in the future, but for now we'll leave the defaults and move on to the mapping definition. Feel free to browse this model and inspect its properties to familiarize yourself with tooling definitions.

Mapping Definition

Mapping Definition Model, view in actual size.

The mapping definition model will let us bind the three models we have so far: the domain, the graphical definition, and the tooling definition. To the right is an image of this model. This is a key model to GMF development and will be used as input to a transformation step which will produce our final model, the generation model.

Continuing on with our cheat sheet, follow the instructions to launch the GMFMap Model wizard. We will again select the 'model' folder to hold our mindmap.gmfmap file and move on to load each of the preselected mindmap.ecore, mindmap.gmfgraph, and mindmap.gmftool models. On the next page, select 'Map' as the Diagram Root Element and finally, make the last page look like the image below.

Cheatsheet map.png


Label mapping.png

One thing we need to do manually is set the Diagram Label property of our Label Mapping to our TopicNameLabel from the graphical definition (yes, this is a temporary feature of the mapping wizard ;). The result should look like the image to the right.

Before moving on, let's pause to describe the mappings. We'll start with the Label Mapping, as it's the one we're looking at here. It's a straightforward mapping, with the Diagram Label property set as we discussed and a mapping to the 'EAttribute name' feature on our Topic element in the domain model.

Moving up to the Node Mapping, we see that our Diagram Node is mapped to the TopicNode of our graphical definition with its corresponding domain model element mapped to our Topic class. The Topic creation tool is also specified in the mapping.

Above the Node Mapping you will find a Top Node Reference. Its Containment Feature is set to the 'EReference rootTopics' feature of our Map class. So, when new Topic nodes are added to the diagram, the instance of our domain Topic will be added to the rootTopics containment reference of our Map class. The label of the node will display the 'name' attribute of the Topic.

The Map class itself is represented by the Canvas. Select the Canvas Mapping element to see this defined, along with the map to the Palette in our tooling definition. Finally, if you select the Link Mapping, you will observe that connections represented by our TopicSubtopicsLink are mapped to the 'EReference subtopics' feature of our Topic class, and are created with our TopicSubtopics Creation Tool.

Tip : Note that it is important to select the proper element when defining mappings at this stage; that is, before GMF does more complete filtering and validation. A good way to ensure you have selected the element you intended (as several may have the same name), open the mapping definition (*.gmfmap) file in a text editor.

Code Generation

Generation Model, view in actual size.

The last model to cover in this tutorial, and the one that is not as critical to understand at this point, is the GMF generator model. See the diagram to the right if you're interested in examining this model.

Now that the minimal graphical elements and mappings are defined, we can generate the code needed to test our work so far. To accomplish this, we will first create a generator model (*.gmfgen) in order to set the properties for code generation, similar to the familiar EMF genmodel. To accomplish this, right-click the mapping file and select 'Create generator model...' as shown below. When prompted, keep the default name 'mindmap.gmfgen'.

Tip : You'll need to have your Java | Compiler | JDK Compliance settings to 1.4 (including Generated .class files compatibility and Source compatibility) when working with GMF.


Create gmfgen.png

Now, we can examine the generator model to see what it includes (if you're the curious type). We'll keep all the default values for now and right-click the mindmap.gmfgen file and select 'Generate diagram code' to proceed. If all goes well, you will see a "Code generation completed successfully." message dialog. Dismiss the dialog, opting to never see it again, and notice the new org.eclipse.gmf.examples.mindmap.diagram plug-in in your workspace.

Up to this point, the models used have been fairly straightforward to edit and understand. The transformation that takes place to create the generator model (*.gmfgen) from the mapping model involves a bit of logic that is important to understand. However, it is not required to understand the details at this point in the tutorial, so additional information can be found here for those interested.

Running the Diagram

Notation Model, view in actual size.

Recall that the runtime uses its own 'notation model' to display and persist the graphical components for your diagram. An image of this model is linked here for those interested.

Now that we have generated the plug-in needed for our diagram, let's launch a new runtime workspace and test the diagram. The default settings of a new Eclipse Application runtime configuration should work fine, while you may opt to run a minimal configuration that includes only your generated plug-ins and their runtime dependencies within an org.eclipse.platform.ide configuration.

Create an empty project and invoke the New... dialog (Ctrl+N). Under 'Examples' you'll notice your new Mindmap Diagram. Create a new diagram and explore its functionality, and look for the creation of the domain model instance as you add and save diagram elements. Of course, we've only specified enough in our diagram definition to allow for simple Topic elements and subtopic links. Next, we'll look at how to add compartments and relationship links...

Basic mindmap.png

Compartments and Connections

Comment.png

Let's return to our diagram definition and add a compartment to our TopicNode to allow for Comment elements to be added. First, add a new child for Comment elements to the Canvas by adding a 'New Child > Child' and name it CommentChild. For its Figure, select your new 'BasicRectangle'. Now we need to add a Compartment to hold the CommentChild elements. To do this, right-click on the Canvas element and select 'New Child > Compartment'. In the properties view, give it a name 'CommentCompartment'. Target your BasicRectangle figure by selecting it for the 'Figure' property.

Compartment.png

While we're here, let's go ahead and add a Connection element, as we'd like to indicate a subtopic relationship between Topic nodes on our diagram. In the Figure Gallery, add a new 'Polyline Connection' with a simple 'BasicLine' name and adjust the other properties as you see fit. Add the link we'll need between topics by right-clicking on the Canvas element and selecting 'New Child > Connection'. Give it the name 'TopicLink', selecting our new BasicLine from the gallery.

Link mapping.png

Now, reopen the mapping model so that we can associate this new link and compartment with our domain elements and assign them tooling. Begin by right-clicking on the Mapping element and selecting 'New Child > Link Mapping'. Fill in the Link Mapping's properties in accordance with the image below, and also add a Creation Tool child element:


In this case, the mapping is rather simple. The 'Diagram Link' maps to our only 'Connection' element, 'TopicLink'. The 'Domain meta information > Target Feature' is required and maps to the 'EReference subtopics' element, meaning that the target of the connection (another Topic element) will be added to this reference list within the source Topic. Finally, our Tool used for creating the links is mapped to the 'Creation Tool TopicSubtopics' element from our tooling definition.

Tip : A level of validation is available for mapping definitions and will take place prior to creation of the generator model. For example, remove the mapping for 'Target Feature' on a Link Mapping and attempt to create the mindmap.gmfgen model. When you do, you will receive an error message indicating that the property is required.

Compartment mapping.png

To explain the mappings, starting with the properties of the 'Compartment Mapping' element, we see that 'Visual representation > Compartment' maps to our only option, 'Compartment Mapping <CommentCompartment>'. The property 'Misc > Child Nodes' was filled in for us when we selected 'CommentCompartment' for the 'Misc > Compartment' property of the 'Child Node Mapping'.

Let's now look at the remainder of its mappings, as shown above. The domain model element 'EClass Comment' is selected for the 'Domain meta information > Element', with its 'EAttribute body' selected for the 'Edit Feature'. As with the Topic mappings described above, this is simply saying that elements of the Comment compartment are representations of Comment domain model instances in a diagram, with their 'body' attribute displaying as the element's editable field in the compartment. The 'Containment Feature' maps to the 'EReference comments' element, as new Comments added to the compartment will be added to this list held within a Topic. Finally, the 'Diagram Node' itself and its 'Tool' map as you would expect to the 'Child CommentChild' and 'Creation Tool Comment' elements, respectively.

Tip : Don't forget to assign a 'Tool' for your mapped diagram elements!


Complink.png


Now we're ready to regenerate the mindmap.gmfgen model and the code for our plug-in. Do this as before and test the new compartment and connection capabilities for the diagram.

Tip : Try this: if you'd like to create a diagram from an existing instance of a domain model, right-click the file and select 'Initialize xxx diagram file' where 'xxx' represents your domain_diagram editor extension. Note that an 'Arrange all' is likely your next step.

Constraints

Link2self.png

Currently, the diagram will allow you to make a subtopic link from one Topic to itself, as seen below. Clearly, this does not make sense for our Mindmap, so we'd like to prevent this somehow.

Tip : Before continuing on with this section, be sure you have copied the antlr.jar file into the 'lib' folder of the plug-in, as referenced on the download page for GMF. The OCL capabilities are temporarily dependent on ANTLR, which is not bundled with GMF. Also, note that the EMF Technology (EMFT) project now has downloads and more information on the OCL and model validation components here.


Link constraint.png

Let's return to our mapping definition, and to the 'Link Mapping' we created earlier. To add a constraint, we begin by right-clicking on the 'Link Mapping' and selecting 'New Child > Link Constraints'. To the Link Constraint, right-click and select 'New Child > Source End Constraint'. The 'Language' property defaults to 'ocl' and we'll need to add the following OCL statement to the 'Body' property: self <> oppositeEnd, as seen in the image below. Then, go through the usual regeneration of mindmap.gmfgen and diagram code and try it out. You will no longer be able to make a link from a Topic to itself.

So, now to explain what is happening here. As you can tell from the context above, we've added a constraint to the creation of a link, based on its source end; that is, the Topic element from which a link is being created. In the OCL we've specified the only condition that will evaluate to true, and therefore allow the link to be created, is the condition where the source element is not equal to the 'oppositeEnd' of the link (the target). In this case, the context of 'self' is the source Topic, and 'oppositeEnd' is a custom variable added to the parser environment for link constraints.

Clearly, this is a very simple constraint, and one that could very well have been defined in the domain model itself and respected by the graphical editor automatically. We will look more closely at constraints in future versions of this tutorial as support for their use matures.

Another Connection

Dependency link def.png

Let's look now at the 'Relationship' element of our domain model. It specifies a number of possible relationships that may be indicated between Topic elements, in addition to the subtopic relationship we have supported thus far. We will add support for this type of Connection, as it will illustrate more completely the properties available for a Link Mapping within GMF.

Returning to our graphical definition model (mindmap.gmfgraph), let's right-click on our gallery and add a 'New Child > Polyline Connection'. Name it 'DependencyLine' and change 'Line Kind' to LINE_DASH. Then add a 'New Child > Target Decoration Polyline Decoration' element to the DependencyLine and name it 'ArrowDecoration'. Now, create a corresponding Connection within our Canvas named 'DependencyLink', selecting our 'DependencyLink' as its 'Figure'.

Dependency link mapping.png

In the mapping definition, create a new 'Link Mapping' and fill in its properties to match what's here:

In this mapping, we'll start with the 'Domain meta information > Element' property. It represents the element represented by this link in the domain, which is simply the 'EClass Relationship' element. Recall that in our previous link mapping, we left this and other properties blank. In that case, our target element for the link was represented by an element (Topic) added to a list of reference held in our source element (also a Topic). In this case, the link is represented in the domain by a class of its own, so more information is required in the link mapping. This class, the Relationship class of the domain model, is contained in a list of references in the Map element, which explains the 'Domain meta feature > Containment Feature' map to 'EReference relations'.

Continuing the mapping description, the 'Label Display Feature' and 'Label Edit Feature' are both mapped to the 'EAttribute label' feature of the Relationship class. The 'Target Feature' in this case is mapped to the 'EReference target' domain model element, indicating that targets of the link are added to this list in the domain when the link is created. Similarly, the 'Source Meta Feature' maps to the 'EReference source' domain model element. And of course, we have our straightforward tool mapping.


Now, we can regenerate our diagram code as before, launch our diagram workspace and test this new link. Below is an example of the results:

Dependency link.png

Summary

As you have seen, using GMF as a means by which to get started creating graphical editors for your domain models is fairly straightforward. We have seen how creating a graphical definition and a mapping definition to the chosen domain can be used to generate much of the basic functionality expected in an EMF/GEF-based editor. In the future, GMF will mature and include more advance capabilities, so check back to see how this tutorial matures along with the project. In the meantime, if you've skipped over links that provide more detail on certain aspects of GMF, now may be the time to do so. Otherwise, feel free to continue with the GMF Tutorial Part 2.

References

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