Difference between pages "Tasking Event-B Overview for D32" and "Tasking Event-B Tutorial"

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imported>Andy
(New page: === Tasking Event-B for D32 === The following text can be read in conjunction with the slides<ref name = "Zurich2010Slides">http://deploy-eprints.ecs.soton.ac.uk/260/2/CGSlidesAndy%2520Edm...)
 
imported>Andy
(New page: THIS PAGE IS UNDER CONSTRUCTION !!!!!! For more information contact Andy Edmunds - University of Southampton - mailto:ae2@ecs.soton.ac.uk === Tasking Event-B Tutorial Overview === This c...)
 
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=== Tasking Event-B for D32 ===
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THIS PAGE IS UNDER CONSTRUCTION !!!!!!
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The following text can be read in conjunction with the slides<ref name = "Zurich2010Slides">http://deploy-eprints.ecs.soton.ac.uk/260/2/CGSlidesAndy%2520Edmunds%2520-%2520Code%2520Generation%2520Slides.pdf</ref> from the Deploy Plenary Meeting - Zurich 2010.
 
  
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Tasking Event-B can be viewed as an extension of the existing Event-B language. We use the existing approaches of refinement and decomposition to structure a project that is suitable for a Tasking Development. During the modelling phase parameters are introduced to facilitate decomposition. As a result of the decomposition process, parameters become part of the interface that enables event synchronization. We make use of this interface and add information (see [[#Implementing Events]]) to facilitate code generation. The tasking extension consists of the constructs in the following table.
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For more information contact Andy Edmunds - University of Southampton - mailto:ae2@ecs.soton.ac.uk
 +
=== Tasking Event-B Tutorial Overview ===
 +
 
 +
This code generation tutorial supplements the Heating Controller tutorial example, and makes use of example projects from the download site. The code generation stage produces implementable Ada code, and also an Event-B project which models the implementation. The Ada code is produced using a pretty printer tool from an intermediate model, the Common Language model (IL1), generated by a translation tool. An overview of Tasking Event-B can be found on the [[Tasking_Event-B_Overview]] page.
 +
 
 +
The Heating Controller development has been refined to the point where we wish to add implementation constructs. The Event-B language is not expressive enough to fully describe the implementation. Tasking Event-B facilitates this final step to implementation, by extending Event-B with the necessary constructs. Event-B machines that are to be implemented (and their seen Contexts) are selected and added to a ''Tasking Development''; the Tasking Development files have the file extension ''.tasking''. The machines in the Tasking Development are then extended with implementation details.
 +
 
 +
The example/tutorial projects are,
  
−
<center>
 
 
{| border="1"
 
{| border="1"
−
|Construct
+
|HeatingController20110429Demo
−
|Options
+
|An example project with a completed Tasking Development and IL1 model (post IL1 translation, but before Event-B translation).
−
|-
 
−
|Machine Type
 
−
|DeclaredTask, AutoTask, SharedMachine
 
 
|-
 
|-
−
|Control
+
|HeatingController20110429Tasking
−
|Sequence, Loop, Branch, EventSynch
+
|Same as the example project above, but with Event-B model translations. The difference being that this development includes a model of the implementation. These are refinements that include a program counter to describe flow of execution in each task.
 
|-
 
|-
−
|Task Type
+
|HeatingController20110429Tutorial
−
|Periodic(n), Triggered, Repeating, OneShot
+
|A bare project for step 1 of the [[Code_Generation_Tutorial#The_Tutorial |tutorial]].
 
|-
 
|-
−
|Priority
+
|HeatingController20110429Tutorial2
−
| -
+
|A partially completed tasking development for steps 2 and 3 of the [[Code_Generation_Tutorial#The_Tutorial |tutorial]].
−
|-
 
−
|Event Type
 
−
|Branch, Loop, ProcedureDef, ProcedureSynch
 
−
|-
 
−
|Parameter Type
 
−
|ActualIn, ActualOut, FormalIn, FormalOut
 
 
|}
 
|}
−
</center>
 
  
−
=== Tasking Developments ===
+
== Preliminaries ==
−
A Tasking Development is modelling component that is generated programmatically, at the direction of the user. The Tasking Development consists of a number of machines (and perhaps associated contexts). We make use of the Event-B EMF extension mechanism <ref name = "EBEMF">[[EMF framework for Event-B]]</ref>, which allows addition of new constructs to a model. The machines in the Tasking Development are extended with the constructs shown in the table, and may be viewed as keywords in a textual representation of the language. With extensions added, a Tasking Development can be translated to a common language model for mapping to implementation source code. There is also a translator that constructs new machines/contexts modelling the implementation, and these should refine/extend the existing elements of the Event-B project.
+
Before further discussion of the modelling aspects, we take a look at the PrettyPrint viewers. The PrettyPrinters make the viewing of IL1 and tasking models easier; it also provides a route to generate source code. The source code can easily be pasted from the IL1 Pretty Printer window into an the Ada source file .
 +
==== The PrettyPrint View of a Tasking Development ====
 +
To open the Tasking PrettyPrint viewer,
 +
* from the top-menu select ''Window/Show View/Other/Tasking Pretty Printer''.
 +
 
 +
Note that the Tasking PrettyPrinter may have to be closed when editing the Tasking Development, since it can give rise to exceptions. The PrettyPrinter would need further work to make it robust, however it is intended only as a short-term solution.
 +
 
 +
* Open the ''SharedBuffer20100819Demo'' Project and switch to the Resource Perspective.
 +
* Open the ''.tasking'' model and inspect it. Clicking on the Main, Machine or Event nodes updates the pretty print window.
 +
 
 +
==== Viewing Source Code ====
 +
aka. The PrettyPrint View of an IL1 Model.
 +
 
 +
To view Ada source code,
 +
* from the top-menu select ''Window/Show View/Other/IL1 Pretty Printer''.
 +
* Open the ''SharedBuffer20100819Demo'' Project and switch to the Resource Perspective.
 +
* Open the ''.il1'' model and inspect it. Clicking on the Protected, Main Entry, or Task nodes updates the pretty print window.
 +
 
 +
==== Cleaning the Tasking Development ====
 +
If the ''.tasking'' file has errors, then it may need cleaning. To do this right-click on the ''Main'' node, select ''Epsilon Translation/CleanUp''. If a model has errors it can still be viewed by clicking on the ''Selection'' tab at the bottom of the tasking editor window.
 +
 
 +
== The Tutorial ==
 +
The steps needed to generate code from an Event-B model, in this tutorial, are as follows,
 +
* Step 1 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Creating_The_Tasking_Development Create the tasking development].
 +
* Step 2 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Providing_the_Annotations_for_Implementations Add annotations]
 +
* Step 3 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Invoking_the_Translation Invoke translators].
 +
 
 +
==== Creating The Tasking Development ====
 +
* Change to the Event-B Perspective.
 +
* Open the ''SharedBuffer20100819Tutorial'' Project.
 +
* Select the following Machines: Reader, Writer and Shared.
 +
* Right-click and select ''Make Tasking Development/Generate Tasking Development''.
 +
 
 +
The new Tasking Development will not be visible in the Event-B perspective, change to the resource perspective, open and inspect the new ''.tasking'' file. The Tasking Development contains (the EMF representation of) the machines that we wish to provide implementations for. In order to introduce the new concepts we have prepared a partially complete development.
 +
 
 +
Change to the Project ''SharedBuffer20100819Tutorial2'' to begin the next step.
 +
 
 +
==== Providing the Annotations for Implementations ====
 +
* Close any Tasking Pretty Print Viewers that remain open. The incomplete model will give rise to exceptions.
 +
* Go to the to the Resource Perspective.
 +
* Open and inspect the ''.tasking'' machine.
 +
 
 +
The ''WriterTsk'' and ''SharedObj'' machines are incomplete. We will take the steps to necessary to provide implementation details.
 +
 
 +
===== The WriterTsk Machine =====
 +
In the partially complete tutorial project we already identified the ''WriterTsk'' as an ''Auto Task'' Tasking Machine, by adding the ''Auto Task'' extension. ''Auto Tasks'' are tasks that will be declared and defined in the ''Main'' procedure of the implementation. The effect of this is that the ''Auto Tasks'' are created when the program first loads, and then activated (made ready to run) before the ''Main'' procedure body runs. We have added the ''Periodic Task'' extension to the ''Auto Task'', and set a period of 250 milliseconds. We will now complete the sequence that has been partially defined in the task body.
 +
 
 +
*'''Add Synchronisation between TWrite and SWrite'''.
 +
** Expand the ''Auto Task Machine'' node.
 +
** Expand the ''Seq'' sub-tree.
 +
** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
 +
** Provide the event label ''w1'' using the properties view.
 +
** Right-click on Event Wrapper and select ''New Child/ Synch Events''.
 +
** Select ''Synch Events'' and go to the drop-down menu of the ''Local Event'' property.
 +
** At this point the drop-down box displays a number of event names, select the ''TWrite'' event.
 +
** Go to the drop-down menu of the ''Remote Event'' property.
 +
** From the list of events select the ''SWrite'' event.
 +
 
 +
The Synch Events construct is used to implement [http://wiki.event-b.org/index.php/Tasking_Event-B_Overview#Control_Constructs Event Synchronisation]. The next step wraps an event in an Event Wrapper in order to update the local state; there is no synchronisation as such but we will re-use the constructs that already exist.
 +
 
 +
*'''Add the Wrapped Event TcalcWVal'''.
 +
** Expand the sub-tree of the second ''Seq'' node.
 +
** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
 +
** Provide the event label ''w2'' using the properties view.
 +
** Right-click on Event Wrapper and select ''New Child/ Synch Events''.
 +
** Select ''Synch Events'' and go to the drop-down menu of the ''Local Event'' property.
 +
** From the list of events select the ''TcalcWVal'' event.
  
−
==== Tasking Machines ====
+
We have now completed the task body, and it just remains to complete provide details for the ''TWrite'' event. The ''TWrite'' event in ''WriterTsk'' is to be synchronized with the ''SWrite'' event in the ''SharedObj''.
−
The following constructs relate only to Tasking Machines, and provide implementation details. Timing of periodic tasks is not modelled formally. Tasking Machines are related to the concept of an Ada task. These can be implemented in Ada using tasks, in C using the pthread library C, or in Java using threads.
+
*'''Add Event Extensions'''.
 +
** Right-click on the ''TWrite'' Event node.
 +
** Select ''New Child/Extension''.
 +
** Right-click on the ''Extension'' node and select ''New Child/Implementation'' from the menu.
 +
** Go to the Implementation properties view and set the ''Implementation Type'' property to ''ProcedureSynch''.
  
−
* Tasking Machines may be characterised by the following types:
+
*'''Identify Incoming and Outgoing parameters'''.
−
** AutoTasks - Singleton Tasks.
+
** Right-click on the ''outAP'' node and add an ''Extension''.
−
** Declared tasks - (Not currently used) A task template relating to an Ada ''tasktype'' declaration.  
+
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
−
** TaskType - Defines the scheduling, cycle and lifetime of a task. i.e. one-shot periodic or triggered. The period of a task is specified in milliseconds.
+
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualOut''.
−
** Priority - An integer value is supplied, the task with the highest value priority takes precedence when being scheduled. For the demonstrator tool the default priority is 5.
+
** Right-click on the ''inAP'' node and add an ''Extension''.
 +
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
 +
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualIn''.
  
−
''Auto Tasks'' are tasks that will be declared and defined in the ''Main'' procedure of the implementation. The effect of this is that the ''Auto Tasks'' are created when the program first loads, and then activated (made ready to run) before the ''Main'' procedure body runs.
+
===== The Shared Machine =====
  
−
==== Shared Machines ====
+
The next step is to identify the ''SharedObj'' machine as a ''Shared Machine''. The ''SharedObj'' Machine will be extended using the Event-B EMF extension mechanism.
−
A Shared Machine corresponds to the concept of a protected resource, such as a monitor. They may be implemented in Ada as a Protected Object, in C using mutex locking, or in Java as a monitor.
+
* Right-click on the ''SharedObj'' Machine node in the ''.tasking'' file.
 +
* Select ''New Child/Extension''.
 +
* Right-click on the ''Extension'' node and select ''New Child/Shared Machine'' from the menu.
  
−
* Applied to the Shared Machine we have:
+
We now show how to extend the ''SWrite'' event of the Shared Machine with details about its implementation. The ''SWrite'' event in ''SharedObj'' is to be synchronized with the ''TWrite'' event in the ''WriterTsk''.
−
** A SharedMachine ''keyword'' that identifies a machine as a Shared Machine.
+
* '''Identify SWrite as a Syncronisation'''.
 +
** Right-click on the ''SWrite'' Event node.
 +
** Select ''New Child/Extension''.
 +
** Right-click on the ''Extension'' node and select ''New Child/Implementation'' from the menu.
 +
** Go to the Implementation properties view and set the ''Implementation Type'' property to ''ProcedureSynch''.
  
−
=== Implementation Specifics ===
+
* '''Identify incoming and outgoing parameters'''.
−
At the stage where we are considering how to implement the Event-B development we need to think about controlling the flow of execution, and how events should be implemented. The following section describes the constructs that we have introduced to facilitate this.
+
** Right-click on the ''inFP'' node and add an ''Extension''.
−
==== Control Constructs ====
+
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
−
Each Tasking Machine has a ''task body'' which contains the flow control (algorithmic constructs).  
+
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''formalIn''.
 +
** Right-click on the ''outFP'' node and add an ''Extension''.
 +
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
 +
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''formalOut''.
  
−
* We have the following constructs available in the Tasking Machine body:
+
===== A Summary of Steps =====
−
** Sequence - for imposing an order on events.
 
−
** Branch - choice between a number of mutually exclusive events.
 
−
** Loop - event repetition while it's guard remains true.
 
−
** Event Synchronisation - synchronization between an event in a Tasking Machine and an event in a Shared Machine. Synchronization corresponds to an subroutine call with atomic (with respect to an external viewer) updates. The updates in the protected resource are implemented by a procedure call to a protected object, and tasks do no share state.  The synchronization construct also provides the means to specify parameter passing, both in and out of the task.
 
−
** Event wrappers - The event synchronization construct is contained in an event wrapper. The wrapper may also contain a single event (we re-use the synchronization construct, but do not use it for synchronizing). The event may belong to the Tasking Machine, or to a Shared Machine that is visible to the task. Single events in a wrapper correspond to a subroutine call in an implementation.
 
  
−
==== Implementing Events ====
+
For a Tasking Machine definition:
−
An event's role in the implementation is identified using the following extensions which are added to the event. Events used in task bodies are 'references' that make use of existing event definitions from the abstract development. The events are extended. to assist with translation, with a keyword indicating their role in the implementation.
+
# Add the Tasking Machine type (Auto etc).
 +
# Add the task type (Periodic etc.).
 +
# Define the task priority.
 +
# Define the task body.
 +
# For each event, add the Event Type.
 +
# For each event parameter, add the Parameter Type.
  
−
* Event implementation.
 
−
** Branch - In essence a task's event is split in the implementation; guards are mapped to branch conditions and actions are mapped to the branch body. If the branch refers to a Shared Machine event (procedureDef) then this is mapped to a simple procedure call.
 
−
** Loop - The task's event guard maps to the loop condition and actions to to loop body. If the loop refers to a Shared Machine event then it is mapped to a simple procedure call.
 
−
** ProcedureSych - This usually indicates to the translator that the event maps to a subroutine, but an event in a task may not require a subroutine implementation if its role is simply to provide parameters for a procedure call.
 
−
** ProcedureDef - Identifies an event that maps to a (potentially blocking) subroutine definition. Event guards are implemented as a conditional wait; in Ada this is an entry barrier, and in C may use a pthread condition variable .
 
  
−
In an implementation, when an subroutine is defined, its formal parameters are replaced by actual parameter values at run-time. To assist the code generator we extend the Event-B parameters. We identify formal and actual parameters in the implementation, and add the following keywords to the event parameters, as follows:
+
For a Shared Machine definition:
 +
# Add the ''SharedMachine'' Machine type.
 +
# For each event, define the Event Type.
 +
# For each event parameter, define the Parameter Type.
  
−
* Event parameter types
+
==== Invoking the Translation ====
−
** FormalIn or FormalOut - event parameters are extended with the ParameterType construct. Extension with formal parameters indicates a mapping to formal parameters in the implementation.
 
−
** ActualIn or ActualOut - Extension with an actual parameter indicates a mapping to an actual parameter in the implementation.
 
  
−
== References ==
+
* To create the IL1 model,
 +
** Right-Click on the Main node, select ''Epsilon Translation/Translate Task Mch 2 IL1 EMF''.
 +
** Open the Resource Perspective.
 +
** Right-click on the ''sharedbuffer20100819Tutorial2'' project folder.
 +
** Select refresh, the ''.il1'' file should appear in the project.
 +
** Open and inspect the file, and view the source code by opening the IL1 Pretty Print view if desired.
  
−
<references/>
+
* To create the Event-B model of the implementation,
 +
** Return to the Rodin Modelling Perspective.
 +
** Right-Click on the Main node, select ''Epsilon Translation/Translate Task Mch 2 Event-B EMF''.
 +
** The ''sharedbuffer20100819bTasking'' project is generated, it can be opened and inspected.
  
 +
There are errors in the generated machines (not investigated the cause yet); these can be fixed in the following way.
 +
* Open a Machine in the Event-B Machine Editor.
 +
* Select the Edit tab.
 +
* Open the REFINES section, the error lies here.
 +
* The correct machine is refined, but choose a different machine to refine (any one, it doesn't matter).
 +
* Select the original refined machine again.
 +
* Save and clean the project, and the error should disappear.
 +
* Repeat for the same errors in the other machines; save and clean again.
 +
* The machines can viewed as normal using the Rodin editors.
  
 
[[Category:User documentation]]
 
[[Category:User documentation]]

Revision as of 15:33, 27 April 2011

THIS PAGE IS UNDER CONSTRUCTION !!!!!!

For more information contact Andy Edmunds - University of Southampton - mailto:ae2@ecs.soton.ac.uk

Tasking Event-B Tutorial Overview

This code generation tutorial supplements the Heating Controller tutorial example, and makes use of example projects from the download site. The code generation stage produces implementable Ada code, and also an Event-B project which models the implementation. The Ada code is produced using a pretty printer tool from an intermediate model, the Common Language model (IL1), generated by a translation tool. An overview of Tasking Event-B can be found on the Tasking_Event-B_Overview page.

The Heating Controller development has been refined to the point where we wish to add implementation constructs. The Event-B language is not expressive enough to fully describe the implementation. Tasking Event-B facilitates this final step to implementation, by extending Event-B with the necessary constructs. Event-B machines that are to be implemented (and their seen Contexts) are selected and added to a Tasking Development; the Tasking Development files have the file extension .tasking. The machines in the Tasking Development are then extended with implementation details.

The example/tutorial projects are,

HeatingController20110429Demo An example project with a completed Tasking Development and IL1 model (post IL1 translation, but before Event-B translation).
HeatingController20110429Tasking Same as the example project above, but with Event-B model translations. The difference being that this development includes a model of the implementation. These are refinements that include a program counter to describe flow of execution in each task.
HeatingController20110429Tutorial A bare project for step 1 of the tutorial.
HeatingController20110429Tutorial2 A partially completed tasking development for steps 2 and 3 of the tutorial.

Preliminaries

Before further discussion of the modelling aspects, we take a look at the PrettyPrint viewers. The PrettyPrinters make the viewing of IL1 and tasking models easier; it also provides a route to generate source code. The source code can easily be pasted from the IL1 Pretty Printer window into an the Ada source file .

The PrettyPrint View of a Tasking Development

To open the Tasking PrettyPrint viewer,

  • from the top-menu select Window/Show View/Other/Tasking Pretty Printer.

Note that the Tasking PrettyPrinter may have to be closed when editing the Tasking Development, since it can give rise to exceptions. The PrettyPrinter would need further work to make it robust, however it is intended only as a short-term solution.

  • Open the SharedBuffer20100819Demo Project and switch to the Resource Perspective.
  • Open the .tasking model and inspect it. Clicking on the Main, Machine or Event nodes updates the pretty print window.

Viewing Source Code

aka. The PrettyPrint View of an IL1 Model.

To view Ada source code,

  • from the top-menu select Window/Show View/Other/IL1 Pretty Printer.
  • Open the SharedBuffer20100819Demo Project and switch to the Resource Perspective.
  • Open the .il1 model and inspect it. Clicking on the Protected, Main Entry, or Task nodes updates the pretty print window.

Cleaning the Tasking Development

If the .tasking file has errors, then it may need cleaning. To do this right-click on the Main node, select Epsilon Translation/CleanUp. If a model has errors it can still be viewed by clicking on the Selection tab at the bottom of the tasking editor window.

The Tutorial

The steps needed to generate code from an Event-B model, in this tutorial, are as follows,

Creating The Tasking Development

  • Change to the Event-B Perspective.
  • Open the SharedBuffer20100819Tutorial Project.
  • Select the following Machines: Reader, Writer and Shared.
  • Right-click and select Make Tasking Development/Generate Tasking Development.

The new Tasking Development will not be visible in the Event-B perspective, change to the resource perspective, open and inspect the new .tasking file. The Tasking Development contains (the EMF representation of) the machines that we wish to provide implementations for. In order to introduce the new concepts we have prepared a partially complete development.

Change to the Project SharedBuffer20100819Tutorial2 to begin the next step.

Providing the Annotations for Implementations

  • Close any Tasking Pretty Print Viewers that remain open. The incomplete model will give rise to exceptions.
  • Go to the to the Resource Perspective.
  • Open and inspect the .tasking machine.

The WriterTsk and SharedObj machines are incomplete. We will take the steps to necessary to provide implementation details.

The WriterTsk Machine

In the partially complete tutorial project we already identified the WriterTsk as an Auto Task Tasking Machine, by adding the Auto Task extension. Auto Tasks are tasks that will be declared and defined in the Main procedure of the implementation. The effect of this is that the Auto Tasks are created when the program first loads, and then activated (made ready to run) before the Main procedure body runs. We have added the Periodic Task extension to the Auto Task, and set a period of 250 milliseconds. We will now complete the sequence that has been partially defined in the task body.

  • Add Synchronisation between TWrite and SWrite.
    • Expand the Auto Task Machine node.
    • Expand the Seq sub-tree.
    • Right-click on the Seq node and select New Child/Left Branch EventWrapper.
    • Provide the event label w1 using the properties view.
    • Right-click on Event Wrapper and select New Child/ Synch Events.
    • Select Synch Events and go to the drop-down menu of the Local Event property.
    • At this point the drop-down box displays a number of event names, select the TWrite event.
    • Go to the drop-down menu of the Remote Event property.
    • From the list of events select the SWrite event.

The Synch Events construct is used to implement Event Synchronisation. The next step wraps an event in an Event Wrapper in order to update the local state; there is no synchronisation as such but we will re-use the constructs that already exist.

  • Add the Wrapped Event TcalcWVal.
    • Expand the sub-tree of the second Seq node.
    • Right-click on the Seq node and select New Child/Left Branch EventWrapper.
    • Provide the event label w2 using the properties view.
    • Right-click on Event Wrapper and select New Child/ Synch Events.
    • Select Synch Events and go to the drop-down menu of the Local Event property.
    • From the list of events select the TcalcWVal event.

We have now completed the task body, and it just remains to complete provide details for the TWrite event. The TWrite event in WriterTsk is to be synchronized with the SWrite event in the SharedObj.

  • Add Event Extensions.
    • Right-click on the TWrite Event node.
    • Select New Child/Extension.
    • Right-click on the Extension node and select New Child/Implementation from the menu.
    • Go to the Implementation properties view and set the Implementation Type property to ProcedureSynch.
  • Identify Incoming and Outgoing parameters.
    • Right-click on the outAP node and add an Extension.
    • Right-click on the Extension and selectNew Child/Parameter Type.
    • Go to the Parameter Type properties view and set the Parameter Type property to actualOut.
    • Right-click on the inAP node and add an Extension.
    • Right-click on the Extension and selectNew Child/Parameter Type.
    • Go to the Parameter Type properties view and set the Parameter Type property to actualIn.
The Shared Machine

The next step is to identify the SharedObj machine as a Shared Machine. The SharedObj Machine will be extended using the Event-B EMF extension mechanism.

  • Right-click on the SharedObj Machine node in the .tasking file.
  • Select New Child/Extension.
  • Right-click on the Extension node and select New Child/Shared Machine from the menu.

We now show how to extend the SWrite event of the Shared Machine with details about its implementation. The SWrite event in SharedObj is to be synchronized with the TWrite event in the WriterTsk.

  • Identify SWrite as a Syncronisation.
    • Right-click on the SWrite Event node.
    • Select New Child/Extension.
    • Right-click on the Extension node and select New Child/Implementation from the menu.
    • Go to the Implementation properties view and set the Implementation Type property to ProcedureSynch.
  • Identify incoming and outgoing parameters.
    • Right-click on the inFP node and add an Extension.
    • Right-click on the Extension and selectNew Child/Parameter Type.
    • Go to the Parameter Type properties view and set the Parameter Type property to formalIn.
    • Right-click on the outFP node and add an Extension.
    • Right-click on the Extension and selectNew Child/Parameter Type.
    • Go to the Parameter Type properties view and set the Parameter Type property to formalOut.
A Summary of Steps

For a Tasking Machine definition:

  1. Add the Tasking Machine type (Auto etc).
  2. Add the task type (Periodic etc.).
  3. Define the task priority.
  4. Define the task body.
  5. For each event, add the Event Type.
  6. For each event parameter, add the Parameter Type.


For a Shared Machine definition:

  1. Add the SharedMachine Machine type.
  2. For each event, define the Event Type.
  3. For each event parameter, define the Parameter Type.

Invoking the Translation

  • To create the IL1 model,
    • Right-Click on the Main node, select Epsilon Translation/Translate Task Mch 2 IL1 EMF.
    • Open the Resource Perspective.
    • Right-click on the sharedbuffer20100819Tutorial2 project folder.
    • Select refresh, the .il1 file should appear in the project.
    • Open and inspect the file, and view the source code by opening the IL1 Pretty Print view if desired.
  • To create the Event-B model of the implementation,
    • Return to the Rodin Modelling Perspective.
    • Right-Click on the Main node, select Epsilon Translation/Translate Task Mch 2 Event-B EMF.
    • The sharedbuffer20100819bTasking project is generated, it can be opened and inspected.

There are errors in the generated machines (not investigated the cause yet); these can be fixed in the following way.

  • Open a Machine in the Event-B Machine Editor.
  • Select the Edit tab.
  • Open the REFINES section, the error lies here.
  • The correct machine is refined, but choose a different machine to refine (any one, it doesn't matter).
  • Select the original refined machine again.
  • Save and clean the project, and the error should disappear.
  • Repeat for the same errors in the other machines; save and clean again.
  • The machines can viewed as normal using the Rodin editors.
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