GuideTutorialMarkedGraph

Tutorial: Make Marked Graph models executable with the GEMOC Studio

What is expected at the end of this tutorial

This tutorial aims at demonstrating the power of the GEMOC studio to define an executable semantics and provide graphical animation for a DSML. It relies of the marked graph language.

The following animation shows the expecting results of this tutorial: according to the fired transitions, tokens move from place to place.

Figure 1. Expected animation for Marked Graph models

Install the projects defining the Marked Graph AS and CS

The domain model is implemented with several EMF projects that you need to import into your workspace. A graphical editor defined with Sirius is also available to visualize and edit Marked Graph models.

Import the Marked Graph AS and CS

Download the provided archive containing the projects and unzip it. Then, with the GEMOC Studio, select import…​ / General / Existing Projects into Workspace and import all the projects from the archive file.

Figure 2. Importing existing projects from the archive file

Here is the archive containing all the projects that will be created during this tutorial.

Abstract Syntax

Marked Graph is a kind of Petri net in which every place has exactly one incoming arc and exactly one outgoing arc. As a consequence, it a concurrent language (several transitions may be fired) and has no conflict.

The Domain Model, also called Abstract Syntax or Metamodel, defines :

• A marked graph as a set of places and transitions.

• Each Place has exactly one input transition and one output transition and a token count.

• A transition has several input places and several output places.

Figure 3. Abstract Syntax (Metamodel) of MarkedGraph

Concrete Syntax and Sample Model

The graphical concrete syntax draws places as circles and transitions as squares. Inputs and outputs of places and transitions are designated by arrows. The following picture shows the graphical representation of the Marked Graph model of wikipedia (using a graphical syntax defined using Sirius).

Figure 4. Example of a Marked Graph model (from wikipedia)

Set up an xDSML project

In this section, we first create an xDSML project for MarkedGraph and initialize it with the provided Abstract Syntax (AS) and Concrete Syntax (CS).

First, check that the current perspective is "xDSML" (top right of Eclipse frame). The perspective can be changed thanks to the menu "Window > Open Perspective > Others".

Create an xDSML Project

Create a "New xDSML project" (New > Project > GEMOC Project / new GEMOC Concurrent xDSML Project).

Figure 5. Create a GEMOC Concurrent xDSML Project

The first dialog of the wizard asks for the name of the project. Define it as org.gemoc.sample.markedgraph.xdsml.

Figure 6. Define the name of the project

Click on Next and define the properties of the language (markedgraph). The 'Package' property is already defined (based on the project name). The othe properties include the name of melange file (used to link together the different parts on an xDSML), the name of the language and the location of the Ecore file. The two other properties 'DSA projects' and 'ECL path' will be created latter in this tutorial.

Use 'markedgraph' for the Melange file name, 'MarkedGraphL' for the Language name and select the markedgraph.ecore file by Browsing the 'org.gemoc.sample.markedgraph.model' project (found in 'model' directory).

Figure 7. Define the properties of the xDSML

Open the Melange file

The Melange file summarizes all the important resources used in an xDSML project (which are part of and managed by other projects). Completion (CTRL-SPACE) can be used to launch wizard but it will not be used in this tutorial. The Melange file is found in the 'org.gemoc.sample.markedgraph.xdsml' project in the 'src' directory.

Figure 8. Content of the Melange file

Define the Execution Semantics

A transition can be fired if there is at least one token in every of each input place. When a transition is fired, one token is removed from each of its input places and one token is added to each of its output places. Several transitions can be fired as the same time.

Defining the execution semantics consists in implementing the previous behavior. In the GEMOC approach, it is split in different concerns:

• The definition of Execution Data (ED) like the runtime count of tokens in a place and Execution Functions (EF) like fire a transition. ED and EF constitute the DSA.

• The definition of the model of concurrency as a set of events and constraints on these events. It is the MoCC concern that is defined in a DSE project (using ECL, Event Constraint Language) possibly completed with MoCCML projects to define libraries of constraints.

• The mapping between the DSA and the MoCC.

In the current version of the GEMOC studio, the MoCC and the mapping are tightly coupled and described in ECL (Event Constraint Language).

Define DSA

During execution of a MarkedGraph, the number of tokens of a place has to be recorded and changed according to the fired transitions. Thus, we have to manage an execution data (ED) called runtimeTokenCount and an execution function (EF) on Transition called fire(). Furthermore, the runtimeTokenCount of each place must be initialized at the start of the execution. It is the purpose of the EF called initialize() on the MarkedGraph element.

The DSA of Marked Graph is composed of :

• one ED called runtimeTokenCount defined on Place . It represents the number of token in a place when the model is executed.

• one EF called initialize() defined on MarkedGraph. It initializes the runtime token count of each place with the initial token count.

• one ED called fire() on Transition. It to remove one token from each of its input places and add one token to all its output places.

Extend the AS with ED and EF

At the moment, we need to complete the AS (markedgraph.ecore) with the ED and EF. In the next release of the GEMOC Studio this step replaced by the use of Melange to automatically extend the AS with ED and EF.

The ED and EF are already defined on the provided metamodel. Thus, there is no need to add the 'runtimeTokenCount' ED on Place, 'fire()' on Transition and 'initialize()' on MarkedGraph.

Figure 9. Abstract Syntax of MarkedGraph extended with Execution Data (ED) and Execution Functions (EF)

Create the DSA Project

In the Project Explorer, right click on any file of the xDSML project and choose GEMOC Languge > Create DSA Project for language to start the wizard.

Figure 10. Create a DSA Project

The wizard first add for the language: select 'MarkedGraphL' and click OK. On the next screen, the project name is already initialized. Click 'Finish' and the 'org.gemoc.sample.markedgraph.k3dsa' is created and the Melange file is completed with references to aspects implemented the ED and EF.

Figure 11. The Melange file with references to aspects implementing ED and EF

Implement the DSA

Open the markedgraphAspects.xtend file. It is located in the org.gemoc.sample.markedgraph.k3dsa project in src/markedgraph.aspects. The file has been initialized with a template that can be discarded and replaced with the following text.

link:MarkedGraph/markedgraph.xtend[role=include]

Figure 12. Definition of the DSA (ED and EF)

There is an error in the Melange file because no aspect has been defined on the NamedElement metaclass. Just comment out the corresponding line.

Figure 13. Corrected Melange file

Define DSE

The purpose of the DSE project is to define events (called DSE) on AS elements that will trigger EF calls when they occurs. Furthermore, constraints can be defined on these events to define when they may occur.

Create the DSE Project

Like for the DSA Project, right click on any file of the xDSML project and choose GEMOC Languge > Create DSE Project for language to start the wizard.

Figure 14. Create a DSE Project

Then :

1. Select the MarkedGraphL language and click OK.

2. On the next screen of the wizard, click Next (the project name is already initialized org.gemoc.sample.markedgraph.dse).

3. On the last screen, complete the required fields:

   • The MarkedGraph Ecore file has already been initialized, just click on Browse.

   • Select the root container : MarkedGraph::MarkedGraph

   • Set the New ECL file basename is already set to 'MarkedGraphL'

Figure 15. Initializing the DSE project

Once the wizard has been completed, the org.gemoc.sample.markedgraph.dse project is created with a template for the MarkedGraphL.ecl file (found in the ecl directory).

Figure 16. Template of the ECL file

Define DSE

Replace the content of the ECL file with the following code (explanations on this code are given bellow):

The file MarkedGraphL.ecl

link:MarkedGraph/MarkedGraphL.ecl[role=include]

Figure 17. Definition of the DSE (events and constraints)

This step has three main purposes:

1. First, it specifies DSE in the context of metaclasses of the AS. For Marked Graph xDSML, we identify 2 DSE:

   • fireIt: defined in the context of a Transition

   • initIt: defined in the context of a MarkedGraph

2. Then, it links them to EF from DSA --- when a DSE will occur the associated EF will be executed.

   • fireIt is linked to the EF 'fire' of Transition

   • initIt is linked to the EF 'initialize' of MarkedGraph

3. Finally, it defines constraints on the DSE to rule the possible scheduling. Constraints generally rely on relations which are defined in MoCC libraries. Here constraints are expressed in CCSL and only relies on relations and expression from the CCSL core library.

   • A first constraint applies on the fireIt events. It is depends on the number of token in a place. Indeed, if there is no tokens, then the fireIt of the output transition can only occur after the fireIt event of the input transition has occured. It is expressed by the first invariant defined in the context of a Place. If there is some tokens in a place, then the fireIt event of the output transition may occur as many times as there is tokens in this place. After, it will only occur when the fireIt on the input transition of the place has occured. It is expressed using the DelayFor expression in the second envariant of Place.

   • Two other constraints are defined in the context of the MarkedGraph element. The first one expresses that the first initIt event must occur before any fireIt event. The second one expresses that the initIt event can occur only one time.

Note

Please notice that, as often, DSE are defined at the language level, but at runtime they are instantiated as MSE on each object instance of the metaclasse they are defined on. For example, there will be one fireIt MSE for each Transition element of MarkedGraph model. For the wikipedia example, there will a fireIt event for transitions t1, t2, t3 and t4. In the same way, constraints apply to the MSE.

Execute a Model

The executable MarkedGraph Language is now defined. We can use the GEMOC Modeling Workbench to execute MarkedGraph models. In the next section, we will see how to define a graphical animation a MarkedGraph model.

Launch the Modeling WorkBench

First, we will create a run configuration. Select "run / run Configurations".

Figure 18. Select "run / run Configurations"

Double click on "Eclipse Application" and change the name "New Configuration" into "MarkedGraph Modeling Workbench".

Figure 19. Define the Marked Graph Modeling Workbench configuration

Then click "Run" to start the new runtime Eclipse which indeed corresponds to the Modeling Workbench for MarkedGraph.

Import the project with a sample model

Import the modeling project org.gemoc.sample.markedgraph.sample in the Modeling Workbench (Import / General / Existing project into Workspace). It contains the wikipedia.markedgraph file which corresponds to the Wikipedia example.

Figure 20. Importing the existing sample project from the archive file

Select the Modeling perspective

• Select "Window / Open Perspective / Others…​". Alternatively, you can click on the little icone on the right of "Quick Access" field, on the left on the current perspective (top right of the main frame).

• Select "Modeling" in the list.

Figure 21. Select the 'Modeling' perspective

View the wikipedia example

To open the graphical visualization of the wikipedia MarkedGraph example, double-click on wikipedia.aird resource, then open the tree view until "wikipedia MarkeGraph diagram" appears. Open it.

Figure 22. Open the Sirius graphical view of wikipedia example

The properties view (bottom right) allow to see the properties on an element. We can see that a place object has the "Runtime Token Count" properties (the added ED).

Create a Launch Configuration

• Select Debug / Debug Configurations

Figure 23. Select Debug / Debug Configurations

• Double click on "Gemoc Concurrent eXecutable Model"

• Change the name of the new configuration to "run wikipedia example"

• Browse to select the model to run (wikipedia.markedgraph)

• Select its language (xDSML field): org.gemoc.sample.markedgraph.xdsml.MarkedGraphL

• Check that the "Decider" is set to "Step by step user decider" (the user will decide which well be the next step to execute).

• Click on "Debug"

Figure 24. Define the configuration to run the wikipedia example

Launch the execution of the model

We can now run the "gemoc" configuration.

It selects the different views related to the execution on an xDSML model.

Figure 25. The wikipedia model is just started

• Logical Steps Decider (top left): the list of the logical steps that may be selected at this execution step. For each step, the trigerred MSE are displayed on the left and the associated EF on the right. The stimuli manager can be used to stop the GEMOC engine, and thus the execution (red button).

Figure 26. Logical Steps Decider

• Stimuli Manager (bottom left): the list of MSE.

• Console (bottom right): several consoles are available. The displayed one is the "Modeling Workbench Console" which reports that the GEMOC Execution has benne started. Change it to the "Default MessagingSystem Console" (click on the arrow near the console symbol). Clear it.

Figure 27. Change the displayed console

• Gemoc Engine Status (with Stimuli Manager): the list on the running GEMOC engines. The red button stops the selected engine.

Figure 28. Gemoc Engine Status

As we have not yet defined any animation for the MarkedGraph Language, there will be no animation and the graphical visualization will not change.

Select a logical step

The Logical Steps view, presents the possible steps, and for each step, the MSE that will occur if it is selected.

Figure 29. Initial State

Double-click on a Logical Step to choose it. The corresponding MSEs occur and trigger the associated execution functions (EF) which make the state of the model evolve. Here, we will see traces in the Console are the EF we have defined print messages. The first MSE was initIt, which init the Graph and all its places (by initializing the runtime token count with the token count). The is then only one possible step: fireIt applied on t1 (__MSE_ta_fireIt).

Figure 30. Execute a logical step (initIt)

Then, we can select a new logical step and so one. In the following screenshots, we have first selected the t1 transition, and then the t2 transition.

Figure 31. Execute a logical step (t1 fired)

Figure 32. Execute a logical step (t2 fired)

Stop the execution

To stop the execution, simply click on the red button in the Logical Steps Decider view (or in the Gemoc Engines view).

How to visualize the state of the model?

It is now time to see how to graphically visualize the evolution on the MarkedGraph model. We can let the second eclipse running and go back to the first one to complete the xDSML definition with the animation part.

Define Animation Viewpoint

During the execution of a Marked Graph model, we want to visualize :

• the number of tokens in any place: the runtime token count will be printed in the circle of one place.

• the firable transitions: they will be drawn in green.

As the animation view is close to the graphical concrete syntax, we extend the existing diagram description.

First, we will define a graphical representation based on the graphical Marked Graph syntax thanks to the wizard called "Create Animator Project for language", then we will add a layer to describe the graphical animation of a Marked Graph model.

Create a debug representation (as an extension of the graphical editor viewpoint)

Run the wizard

Rigth-click on any file of the org.gemoc.sample.markedgraph.xdsml project and select GEMOC Language > Create Animator Project for language.

Figure 33. Launch the Animator wizard

On the first screen of the wizad, select "Extends an existing diagram description".

Figure 34. Select "Extends an existing diagram description"

Select the viewpoint to extend "MarkedGraph diagram".

Figure 35. Select the viewpoint to extend

Finally, we can fill in the Project Name in which the newly creating viewpoint file will take place (org.gemoc.sample.markedgraph.animation), the name of the viewpoint file (markedgraph-animation.odesign), the viewpoint name (MarkedGraphAnimationViewpoint) and the diagram name (MarkedGraphAnimation).

Figure 36. Information of the animation viewpoint

The last screen allows to choose the name of the layer to be created. Debug is a good name.

Press Finish to create the project. The markedgraph-animation.odesign file is opened.

Open the markedgraph-animation.odesign

Open the markedgraph-animation.odesign file and unfold its content.

Figure 37. Initial makedgraph-animation.odesign file

Load markedgraph.odesign as a resource.

To be able to complete the definition of the odesign file, we first need to load the existing markedgraph.odesign as a resource :

• Right click in the markedgraph-animation.odesign editor to select Load Resource…​.

• Select Browse workspace…​

• Select markedgraph.odesign in the org.gemoc.sample.markedgraph.design project

• Click OK

• Click OK

Add markedgraph.ecore to the metamodels

• Select "Diagram Extension MarkedGraph" element.

• In the Properties view, select metamodels.

• Click on "Add from workspace".

• Select "markedgraph.ecore" (unfold the project structure)

• Click OK

Complete the debug representation

On the "Mapping Based Decoration Enabled breakpoint" and "Mapping Based Decoration Disabled breakpoint", select the "Place" and "Transition" element.

The debug view will show a symbol on the Place and Transition to show whether the corresponding breakpoint is enabled or disabled.

Create an animation representation

After the debug presentation has been defined, we can complete it to add an animation layer.

Create the Animation Layer

• Right click on "Diagram extension MarkedGraph" to select New Diagram Element / Additional Layer.

• Set its "id" to "Animation".

Display the firable transition with a green background color

• Right click on "Animation" to select "New Customization / Style Customizations".

• Right click on "Style Customizations" to select "New Customization / Style Customization".

• On "Style Customization", set the "Predicate Expression" to:

  [self.eGet('inputs')->forAll(p | p.eGet('runtimeTokenCount').toString().toInteger() > 0) /]

• Right click on "Style Customization" to select "New Customization / Property Customization (by selection)"

• For "Applied On" property, select "Square white".

• For "Property Name", set "color" (completion is available with CTRL-SPACE)

• For "Value Selection", set "light_green"

Set the background color of a place to light_yellow

Perform the same action as above to set the background color of places to yellow.

Display the runtime token count in a place

• Right click on "Style Customization" to select "New Customization / Property Customization (by expression)"

• For "Applied On" property, select "Ellipse white".

• For "Property Name", set "labelExpression" (completion is available with CTRL-SPACE)

• For "Value Selction", set "feature:runtimeTokenCount"

Add the Animation service

• Right click on "MarkedGraphAnimationViewpoint" to select "New Extension / Java Extension".

• Set "Qualified Class Name" to "org.gemoc.sample.markedgraph.animation.services.MarkedgraphAnimationServices".

In the project, org.gemoc.sample.markedgraph.animation project, in src/org.gemoc.sample.markedgraph.animation.services, copy the MarkedgraphDebugServices.java file to MarkedgraphAnimationServices.java. Then, change AbstractGemocDebuggerServices to AbstractGemocAnimatorServices in its source code (two times: import and extends). Finally, change "Debug" to "Animation".

Animate a Model

The executable MarkedGraph Language is now defined with a graphical visualization.

Restart the MarkedGraph Modeling WorkBench

First of all, we need to restart (File > restart) the second eclipse so that the new projects are available.

Add the MarkedGraphAnimationViewpoint to wikipedia.aird

Right click on wikipedia.aird and select Viewpoints Selection.

Select Viewpoint Selection

Select MarkedGraphAnimationViewpoint

You can now open the wikipedia graphical representation (wikipedia.air / Representation per category / markedgraph / MarkedGraph diagram / wikipedia MarkedGraph diagram). On the visualization, all places should be with a yellow background.

If it does not work with the "Modeling" perpective, retry with the "Sirius" perspective and then come back to the "Modeling" perspective.

Update the "run wikipedia example" configuration

Open the "run wikipedia example" configuration" (Debug > Debug Configuration…​). Complete the "Animator" field with "/org.gemoc.sample.markedgraph.sample/wikipedia.aird" (use Browse to select it).

First, we will create a run configuration. Select "run / run Configurations"

Launch the execution of the model

We can now run the "gemoc" configuration (using debug). It opens the different views we have already seen but also the graphical visualization on the model.

Going further…​

To improve readability of the ECL file and also to favor capitalization and reuse of MoCC elements, it is possible (and encouraged) to define libraries. Those libraries looks like the predefined ones that we have already used like kernel.lib and CCSL.lib.

Define a MoCCML library using CCSL

Using the GEMOC Studio, we start by defining a MoCCML project. In the xDSML view, we select Behavioral definition / MoCC definition library to create this new project.

We can then define in this project the following markedgraph.ccslLib file. TODO: To be corrected.

The file markedgraph.ccslLib defining a MoCCML library

link:MarkedGraph/markedgraph.ccslLib[role=include]

Using it in the ECL file

To use this new library, we only have to import it at the beginning of the ECL file and the we can use it as kernel.lib and CCSL.lib libraries.

Here is the new ECL file.

The file MarkedGraphL.ecl using the MoCCML library

link:MarkedGraph/markedgraph-library.ecl[role=include]

Use constraint automata to define the MoCC

Sometimes, it may be easier to define the MoCC using automata. For example, we can see a place as something on which we can read a token (ont output transition reads one token) or we can write a token (one input transition writes one token). A token can only be read if there is at least one in the place. Initially, there is as much token in the place as in the initial token count of the place.

Define the constraint automaton using MoCCML editor

For explanations on how to use the MoCCML editor, please refer to the GEMOC manual.

We first define the declaration of a relation (placeReadWrite). Here after is its graphical representation. This relation is parameterized by the r clock (some one how wants to read a token), the w clock (someone how wants to write a token, and n the initial count of token in the place).

Figure 38. Graphical declaration of the placeReadWriteDef relation

Then we can define this relation. Here after is the resulting automaton. The local variable count represent the number of tokens in this place. s0 is the initial state. The action on the transition from s0 to s initialize count with n (the parameter). The two reflexive transitions on s explain what happens when w or r occurs. The write transition is fired when w occurs and a token is assed in the place (count is incremented). The read transition is fired when r occurs. It removes a token and thus decrements count. A guard prevents the read transition to be fired if there is not at liste one token in the place (count >= one).

Figure 39. Automaton defining the placeReadWriteDef relation.

Here is the textual representation of this constraint automata.

Textual representation of the constraint automata.

link:MarkedGraph/markedgraph.moccml[role=include]