Difference between revisions of "Tasking Event-B Tutorial"

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(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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THIS PAGE IS UNDER CONSTRUCTION !!!!!!
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For more information contact Andy Edmunds - University of Southampton - mailto:ae2@ecs.soton.ac.uk
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<< I AM UPDATING THIS PAGE >>
  
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For more information contact Andy Edmunds - University of Southampton - mailto:ae2@ecs.soton.ac.uk
 
 
=== Tasking Event-B Tutorial Overview ===
 
=== 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.
+
This tutorial follows on from the abstract development described [http://wiki.event-b.org/index.php/Development_of_a_Heating_Controller_System here].
  
−
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.
+
This code generation tutorial extends the Heating Controller tutorial example, and makes use of example projects from the download site. The code generation stage produces Java code, and also an Event-B model. It is a model of the implementation, and contains flow control variables that model the flow of execution through the task body. The Java code is produced from an intermediate model that is not visible to the user. The Common Language model (CLM), is generated from the Tasking Event-B by a translation tool. Java (and other implementations) may be generated from the CLM. An overview of Tasking Event-B can be found [http://wiki.event-b.org/index.php/Tasking_Event-B_Overview here].
  
−
The example/tutorial projects are,
+
In the example so far, the Heating Controller 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 modelling tasks, shared objects and the environment are identified, and  extended with the appropriate implementation details.
 +
 
 +
The example/tutorial projects are are available from [https://github.com/andyed2003/codeGenExamples Git] or clone [https://github.com/andyed2003/codeGenExamples.git this].
  
 
{| border="1"
 
{| border="1"
−
|HeatingController20110429Demo
+
|Heating_ControllerTutorial2_Completed
−
|An example project with a completed Tasking Development and IL1 model (post IL1 translation, but before Event-B translation).
+
|An example project with an environment simulation. The environment variables are monitored and controlled using subroutine calls. The project contains a complete Tasking Development with generated Event-B and Java code.
 
|-
 
|-
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|HeatingController20110429Tasking
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|Heating_ControllerTutorial2_Partial1
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|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.
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|A project with the final decomposition completed, ready to begin Tasking Event-B Development.  
 
|-
 
|-
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|HeatingController20110429Tutorial
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|Heating_ControllerTutorial2_Partial2
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|A bare project for step 1 of the [[Code_Generation_Tutorial#The_Tutorial |tutorial]].
+
|A partially completed tasking specification for the continuation of the tutorial.
 
|-
 
|-
−
|HeatingController20110429Tutorial2
+
|TheoriesForCG
−
|A partially completed tasking development for steps 2 and 3 of the [[Code_Generation_Tutorial#The_Tutorial |tutorial]].
+
|Contains the mathematical language translations; encoded as rules in a theory plug-in rule-base.
 
|}
 
|}
  
−
== Preliminaries ==
+
== Using the Tasking Extension ==
−
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 steps needed to generate code from an Event-B model, in this tutorial, are as follows,
−
==== The PrettyPrint View of a Tasking Development ====
+
* Step 1 - [[Tasking Event-B_Tutorial#Adding the Implementation Level Refinement|Adding the Implementation Level Refinement]]
−
To open the Tasking PrettyPrint viewer,
+
* Step 2 - [[Tasking Event-B_Tutorial#Pre-processing|Pre-processing]]
−
* from the top-menu select ''Window/Show View/Other/Tasking Pretty Printer''.
+
* Step 3 - [[Tasking Event-B_Tutorial#Adding Tasking Event-B|Add Tasking annotations]].
 +
* Step 4 - [[Tasking Event-B_Tutorial#Invoking the Translation|Invoke translators]].
 +
=== Download and Copy the Theories ===
 +
The translations of the Event-B mathematical language to the target language constructs are specified as rules in the theory plug-in. Example rule files are included for the example, and are available in MathExtension from the [https://github.com/andyed2003/codeGenTheoryRepo Git] repository, or clone [https://github.com/andyed2003/codeGenTheoryRepo.git this]. After checking out the theories, they must be un-deployed, then re-deployed, ensuring that the builder creates all of the appropriate files. Right-Click on the theory file and select deploy to do this. If you already have a MathExtensions folder then it should be renamed else the import will be prevented. Files from this folder can be copied and deployed in the new folder if necessary.
 +
 
 +
=== Adding the Implementation Level Refinement ===
 +
The final decomposition generates the machines that are required for code generation. However, it is not possible to edit the machines since they are machine generated, and therefore this is prohibited. In order to be able to modify the models we will refine the generated machines. This is where we begin with the ''Heating_ControllerTutorial2_Partial1'' project (Where the pre-processing steps, described below, have been performed already). To refine the machines we can use the automatic refinement feature, but this presents us with two problems that are dealt with in the pre-processing steps.  
  
−
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.
+
=== Pre-processing ===
  
−
* Open the ''SharedBuffer20100819Demo'' Project and switch to the Resource Perspective.
+
The pre-processing step, described here, is done automatically by the tool. The description is provided to assist with understanding the changes that occur to a model, during the code generation phase.
−
* Open the ''.tasking'' model and inspect it. Clicking on the Main, Machine or Event nodes updates the pretty print window.
 
  
−
==== Viewing Source Code ====
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* The Code Generator requires a flattened, and annotated, version of each machine; all of the Event-B elements are made available in the implementation level machine.  
−
aka. The PrettyPrint View of an IL1 Model.
 
  
−
To view Ada source code,
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===== 'Flattening' the Implementation Machines =====
−
* 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 ====
+
* Events are changed to be ''not extended''.
−
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.
+
* Abstract invariants are copied to the implementation level machine.
  
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== The Tutorial ==
+
===== Annotations are provided automatically =====
−
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].
+
* Typing annotations are added to typing invariants and axioms where they type variables and constants.
−
* Step 2 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Providing_the_Annotations_for_Implementations Add annotations]
+
* Parameter directions (in or out) are inferred from the events.
−
* Step 3 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Invoking_the_Translation Invoke translators].
+
 
 +
=== Manually correcting the Composed Machine ===
  
−
==== Creating The Tasking Development ====
+
The hierarchy created by successive machine decompositions gives rise to a tree of refined events. Only the leaf event nodes are used during code generation. In the current code generator there is no algorithm to navigate this tree automatically. Therefore the composed machine points to the incorrect machines and events.
−
* 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.  
+
We must manually change the composed machine to address this problem.
  
−
Change to the Project ''SharedBuffer20100819Tutorial2'' to begin the next step.
+
* Modify the lowest level decomposed machine, HCtrl_M1_cmp, to ''include'' the implementation level machines (task names ending in *Impl). To do this,
 +
* open the composed machine editor. Open the INCLUDES edit feature.
 +
* Select the second drop-down box and find the *Impl version of each machine.
 +
* Save the composed machine.
 +
* Now add missing synchronizations to the composed machine. Add the ''Envir1Impl'' to the includes of HCtrl_M1_cmp.
 +
* Each composed event in the task, that synchronizes with the Environ machine, must have the remote event synchronization added manually. This can only be done by inspection of each composed event. We need to update Sense_Temperatures, Display_Current_Temperature, Actuate_OverHeat_Alram, Actuate_Heat_Source, Sense_Heater_Status, Actuate_NoHeat_Alarm, Sense_PressIncrease_Target_Temperature, Sense_PressDecrease_Target_Temperature, Display_Target_Temperature. One by one, expand the events in the composed events section of the composed machine editor; add a new event in the combines events section, select ''Envir1Impl'' and add the synchronizing event from the list-box to the right.
  
−
==== Providing the Annotations for Implementations ====
+
=== Removing Non-deterministic Constructs ===
−
* 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.  
+
It is also at this stage that any remaining non-deterministic constructs should be removed by replacing them with deterministic constructs.
  
−
===== The WriterTsk Machine =====
+
TIP: Non-deterministic constructs cause strange characters to appear in the source code. If you see strange characters in the generated code, check for non-deterministic constructs in the implementation level machines.
−
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'''.
+
Alter_Temperature_Sensor1 in Envir1Impl: action becomes ts1 := ts1 + 1
−
** Expand the ''Auto Task Machine'' node.
+
Alter_Temperature_Sensor2 in Envir1Impl: action becomes ts1 := ts1 + 1
−
** Expand the ''Seq'' sub-tree.
+
Alter_Heater_Status in Envir1Impl: action becomes hss := FALSE
−
** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
+
INITIALISATION in Heater_Monitor_TaskImpl: becomes shs := FALSE
−
** 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.
+
=== Adding Tasking Event-B ===
  
−
*'''Add the Wrapped Event TcalcWVal'''.
+
*Setting Context attributes.
−
** Expand the sub-tree of the second ''Seq'' node.
+
**Using the project ''Heating_ControllerTutorial2_Partial1''.  
−
** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
+
**Open the context, select the Tasking Context drop-down box, and select Tasking, as the type for the context.  
−
** 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''.
+
Each Machine should be completed as follows.
−
*'''Add Event Extensions'''.
+
==== The Temp_Ctrl_TaskImpl Machine ====
−
** Right-click on the ''TWrite'' Event node.
+
During this part of the tutorial we will cut and paste from ''Heating_ControllerTutorial2_Completed'' model when, specifying the task bodies, to save typing. We use the 'Event-B Machine Editor' to edit the Tasking Event-B.
−
** 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'''.
+
*In the Tasking section of the Event-B editor, click on + to add a new Machine Type construct.
−
** Right-click on the ''outAP'' node and add an ''Extension''.
+
**The machine type defaults to ''Auto Task''.
−
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
+
**Click on the right-arrow symbol by ''Machine Type''.
−
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualOut''.
+
**Add a new Task Type section by clicking on its green + symbol.
−
** Right-click on the ''inAP'' node and add an ''Extension''.
+
**A Machine Type element is added. The task type defaults to ''Periodic''
−
** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
+
**Set a period of 250 milliseconds.  
−
** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualIn''.
+
*'''Add a new TaskBody'''.
 +
**Add a new Task Body section by clicking on its green + symbol.
 +
**Copy and paste the task body from ''Heating_ControllerTutorial2_Completed/Temp_Ctrl_TaskImpl''
 +
**Save the model. Ignore the highlighted typing errors, since these annotations will be added by the code generator during pre-processing.
  
−
===== The Shared Machine =====
+
''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 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.
+
==== The Shared Machine ====
−
* 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''.
+
The next step is to identify the ''Shared_ObjectImpl'' machine as a ''Shared Machine''.
−
* '''Identify SWrite as a Syncronisation'''.
+
*Open the Tasking Section.
−
** Right-click on the ''SWrite'' Event node.
+
*Add a Machine Type by clicking +.
−
** Select ''New Child/Extension''.
+
* Select ''Shared'' in the Machine Type drop Down box.
−
** 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'''.
+
==== The Environ Machine ====
−
** Right-click on the ''inFP'' node and add an ''Extension''.
+
We identify the ''Envir1Impl'' as an ''Environ Machine'',
−
** 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 ''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''.
 
  
−
===== A Summary of Steps =====
+
*Click on +,  in the Machine Editor, to add a to add a Tasking Section.
 +
*A Machine Type element is created.
 +
*Select ''Environ Machine'' in the drop down box.
  
−
For a Tasking Machine definition:
+
*In the Tasking section of the Event-B editor, click on + to add a new Machine Type construct.
−
# Add the Tasking Machine type (Auto etc).
+
**The machine type defaults to ''Auto Task'', change it to ''Environ''.
−
# Add the task type (Periodic etc.).
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**Click on the right-arrow symbol by ''Machine Type''.
−
# Define the task priority.
+
**Add a new Task Type section by clicking on its green + symbol.
−
# Define the task body.
+
**A Machine Type element is added. The task type defaults to ''Periodic''
−
# For each event, add the Event Type.
+
**Set a period of 100 milliseconds.  
−
# For each event parameter, add the Parameter Type.
+
*'''Add a new TaskBody'''.
 +
**Add a new Task Body section by clicking on its green + symbol.
 +
**Copy and paste the task body from ''Heating_ControllerTutorial2_Completed/Envir1Impl''
 +
**Save the model.
  
 +
In the implementation, ''Environ Tasks'' are declared and defined in the ''Main'' procedure . The ''Envir1Impl'' machine models a task that simulates the environment, and can be used to generate simulation code. For deployment in a non-simulated environment the environ machine's generated code can be ignored. To specify the Environment task's behaviour we add edit the task body.
  
−
For a Shared Machine definition:
+
When saving, the task body text is sent to the parser. If parsing is successful then a builder adds the structure to the underlying EMF tree. If parsing fails then an error panel displays the source of the error.
−
# Add the ''SharedMachine'' Machine type.
 
−
# For each event, define the Event Type.
 
−
# For each event parameter, define the Parameter Type.
 
  
−
==== Invoking the Translation ====
+
== Invoking the Translators ==
  
−
* To create the IL1 model,
+
* To generate code,
−
** Right-Click on the Main node, select ''Epsilon Translation/Translate Task Mch 2 IL1 EMF''.
+
** Right-Click on the composed machine, or any tasking machine in the development, select ''Code Generation/Translate Event-B to xx'' where ''xx'' is the chosen language.
−
** Open the Resource Perspective.
+
** Open the generated ''code'' directory in the project to view the source files.  
−
** 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,
 
* To create the Event-B model of the implementation,
−
** Return to the Rodin Modelling Perspective.
+
** Right-Click on the composed machine, or any tasking machine in the development, select ''Code Generation/Translate Tasking Event-B to Event-B''.
−
** Right-Click on the Main node, select ''Epsilon Translation/Translate Task Mch 2 Event-B EMF''.
+
** The Event-B model should be updated with the flow control variables. Users are not able to manually edit the generated elements. The additions can be removed using the menu option ''Code Generation/Remove Generated Event-B''
−
** 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.
 
  
 +
=== Generated Code ===
 +
Generated code will be visible in the code directory, in the Event-B project. However a refresh of the workspace is required. The directory is visible in the resource view; or alternatively, click on the view menu in the Event-B perspective, select customize view, and uncheck the ''all file and folders'' filter.
 
[[Category:User documentation]]
 
[[Category:User documentation]]

Latest revision as of 12:41, 2 September 2013

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

<< I AM UPDATING THIS PAGE >>

Tasking Event-B Tutorial Overview

This tutorial follows on from the abstract development described here.

This code generation tutorial extends the Heating Controller tutorial example, and makes use of example projects from the download site. The code generation stage produces Java code, and also an Event-B model. It is a model of the implementation, and contains flow control variables that model the flow of execution through the task body. The Java code is produced from an intermediate model that is not visible to the user. The Common Language model (CLM), is generated from the Tasking Event-B by a translation tool. Java (and other implementations) may be generated from the CLM. An overview of Tasking Event-B can be found here.

In the example so far, the Heating Controller 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 modelling tasks, shared objects and the environment are identified, and extended with the appropriate implementation details.

The example/tutorial projects are are available from Git or clone this.

Heating_ControllerTutorial2_Completed An example project with an environment simulation. The environment variables are monitored and controlled using subroutine calls. The project contains a complete Tasking Development with generated Event-B and Java code.
Heating_ControllerTutorial2_Partial1 A project with the final decomposition completed, ready to begin Tasking Event-B Development.
Heating_ControllerTutorial2_Partial2 A partially completed tasking specification for the continuation of the tutorial.
TheoriesForCG Contains the mathematical language translations; encoded as rules in a theory plug-in rule-base.

Using the Tasking Extension

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

Download and Copy the Theories

The translations of the Event-B mathematical language to the target language constructs are specified as rules in the theory plug-in. Example rule files are included for the example, and are available in MathExtension from the Git repository, or clone this. After checking out the theories, they must be un-deployed, then re-deployed, ensuring that the builder creates all of the appropriate files. Right-Click on the theory file and select deploy to do this. If you already have a MathExtensions folder then it should be renamed else the import will be prevented. Files from this folder can be copied and deployed in the new folder if necessary.

Adding the Implementation Level Refinement

The final decomposition generates the machines that are required for code generation. However, it is not possible to edit the machines since they are machine generated, and therefore this is prohibited. In order to be able to modify the models we will refine the generated machines. This is where we begin with the Heating_ControllerTutorial2_Partial1 project (Where the pre-processing steps, described below, have been performed already). To refine the machines we can use the automatic refinement feature, but this presents us with two problems that are dealt with in the pre-processing steps.

Pre-processing

The pre-processing step, described here, is done automatically by the tool. The description is provided to assist with understanding the changes that occur to a model, during the code generation phase.

  • The Code Generator requires a flattened, and annotated, version of each machine; all of the Event-B elements are made available in the implementation level machine.
'Flattening' the Implementation Machines
  • Events are changed to be not extended.
  • Abstract invariants are copied to the implementation level machine.
Annotations are provided automatically
  • Typing annotations are added to typing invariants and axioms where they type variables and constants.
  • Parameter directions (in or out) are inferred from the events.

Manually correcting the Composed Machine

The hierarchy created by successive machine decompositions gives rise to a tree of refined events. Only the leaf event nodes are used during code generation. In the current code generator there is no algorithm to navigate this tree automatically. Therefore the composed machine points to the incorrect machines and events.

We must manually change the composed machine to address this problem.

  • Modify the lowest level decomposed machine, HCtrl_M1_cmp, to include the implementation level machines (task names ending in *Impl). To do this,
  • open the composed machine editor. Open the INCLUDES edit feature.
  • Select the second drop-down box and find the *Impl version of each machine.
  • Save the composed machine.
  • Now add missing synchronizations to the composed machine. Add the Envir1Impl to the includes of HCtrl_M1_cmp.
  • Each composed event in the task, that synchronizes with the Environ machine, must have the remote event synchronization added manually. This can only be done by inspection of each composed event. We need to update Sense_Temperatures, Display_Current_Temperature, Actuate_OverHeat_Alram, Actuate_Heat_Source, Sense_Heater_Status, Actuate_NoHeat_Alarm, Sense_PressIncrease_Target_Temperature, Sense_PressDecrease_Target_Temperature, Display_Target_Temperature. One by one, expand the events in the composed events section of the composed machine editor; add a new event in the combines events section, select Envir1Impl and add the synchronizing event from the list-box to the right.

Removing Non-deterministic Constructs

It is also at this stage that any remaining non-deterministic constructs should be removed by replacing them with deterministic constructs.

TIP: Non-deterministic constructs cause strange characters to appear in the source code. If you see strange characters in the generated code, check for non-deterministic constructs in the implementation level machines. 

Alter_Temperature_Sensor1 in Envir1Impl: action becomes ts1 := ts1 + 1
Alter_Temperature_Sensor2 in Envir1Impl: action becomes ts1 := ts1 + 1
Alter_Heater_Status in Envir1Impl: action becomes hss := FALSE
INITIALISATION in Heater_Monitor_TaskImpl: becomes shs := FALSE

Adding Tasking Event-B

  • Setting Context attributes.
    • Using the project Heating_ControllerTutorial2_Partial1.
    • Open the context, select the Tasking Context drop-down box, and select Tasking, as the type for the context.

Each Machine should be completed as follows.

The Temp_Ctrl_TaskImpl Machine

During this part of the tutorial we will cut and paste from Heating_ControllerTutorial2_Completed model when, specifying the task bodies, to save typing. We use the 'Event-B Machine Editor' to edit the Tasking Event-B.

  • In the Tasking section of the Event-B editor, click on + to add a new Machine Type construct.
    • The machine type defaults to Auto Task.
    • Click on the right-arrow symbol by Machine Type.
    • Add a new Task Type section by clicking on its green + symbol.
    • A Machine Type element is added. The task type defaults to Periodic
    • Set a period of 250 milliseconds.
  • Add a new TaskBody.
    • Add a new Task Body section by clicking on its green + symbol.
    • Copy and paste the task body from Heating_ControllerTutorial2_Completed/Temp_Ctrl_TaskImpl
    • Save the model. Ignore the highlighted typing errors, since these annotations will be added by the code generator during pre-processing.

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

The next step is to identify the Shared_ObjectImpl machine as a Shared Machine.

  • Open the Tasking Section.
  • Add a Machine Type by clicking +.
  • Select Shared in the Machine Type drop Down box.

The Environ Machine

We identify the Envir1Impl as an Environ Machine,

  • Click on +, in the Machine Editor, to add a to add a Tasking Section.
  • A Machine Type element is created.
  • Select Environ Machine in the drop down box.
  • In the Tasking section of the Event-B editor, click on + to add a new Machine Type construct.
    • The machine type defaults to Auto Task, change it to Environ.
    • Click on the right-arrow symbol by Machine Type.
    • Add a new Task Type section by clicking on its green + symbol.
    • A Machine Type element is added. The task type defaults to Periodic
    • Set a period of 100 milliseconds.
  • Add a new TaskBody.
    • Add a new Task Body section by clicking on its green + symbol.
    • Copy and paste the task body from Heating_ControllerTutorial2_Completed/Envir1Impl
    • Save the model.

In the implementation, Environ Tasks are declared and defined in the Main procedure . The Envir1Impl machine models a task that simulates the environment, and can be used to generate simulation code. For deployment in a non-simulated environment the environ machine's generated code can be ignored. To specify the Environment task's behaviour we add edit the task body.

When saving, the task body text is sent to the parser. If parsing is successful then a builder adds the structure to the underlying EMF tree. If parsing fails then an error panel displays the source of the error.

Invoking the Translators

  • To generate code,
    • Right-Click on the composed machine, or any tasking machine in the development, select Code Generation/Translate Event-B to xx where xx is the chosen language.
    • Open the generated code directory in the project to view the source files.
  • To create the Event-B model of the implementation,
    • Right-Click on the composed machine, or any tasking machine in the development, select Code Generation/Translate Tasking Event-B to Event-B.
    • The Event-B model should be updated with the flow control variables. Users are not able to manually edit the generated elements. The additions can be removed using the menu option Code Generation/Remove Generated Event-B

Generated Code

Generated code will be visible in the code directory, in the Event-B project. However a refresh of the workspace is required. The directory is visible in the resource view; or alternatively, click on the view menu in the Event-B perspective, select customize view, and uncheck the all file and folders filter.

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