Difference between pages "Code Generation Tutorial" and "Event-B Classdiagrams"

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imported>Colin
 
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'''This Page is Under Construction!!!!'''
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''this page is under construction''
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[[Image:IUMLB_big.png|frame|left]]
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{{TOCright}}
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==Introduction==
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In iUML-B, Class diagrams are used to define and visualize entity-relationship data models. They can be added to Event-B Machines and Event-B Contexts and visualize given sets , constants and variables. Diagram elements elaborate pre-existing user data in order to visualize it. The diagram defines type, sub-type and further constraint information for the data by generating invariants or axioms.
  
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=== Tutorial Overview ===
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==Principles of Operation==
  
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The aim of the tutorial is to allow users to explore the approach with a relatively simple example. The example uses a shared buffer with reader and writer processes. The tutorial is presented in three stages, making use of the example projects from the download site. There are two translations performed, one is to a common language model (IL1). The second is to an Event-B project which includes a model of the implementation. There is a PrettyPrinter for Ada source code, which uses the common language model. An overview of Tasking Event-B can be found at http://wiki.event-b.org/index.php/Tasking_Event-B_Overview.
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Classes, Attributes and Associations are all model elements that represent data. They can be linked to existing Event-B data elements: Variables, Constants or (for Classes only) Carrier Sets. This relationship is called ''Elaborates'' because the diagram element elaborates properties of the data item. Any data element within scope, locally within the same machine or context, or via sees and extends, can be elaborated. As a short cut, a button is provided to create a new data item and link to it in one step.  
  
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A typical Event-B development may be refined to the point where it is ready for implementation, but 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.
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Class diagrams can be added to Machines or Contexts, but note that some features are not available when in a Context (e.g. only constants and sets are within scope to link to and methods cannot be used in classes).
  
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The example/tutorial projects are,
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Methods can be placed inside Classes and link (elaborate) one or more events in the containing Machine. This means that the elaborated events are given a paramter representing the class instance (similar to 'this' or 'self' in programming languages). When in variable classes (i.e. a class that elaborates a variable) methods may be constructors or destructors.
  
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{| border="1"
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===Main Data Elements of a Class Diagram===
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|SharedBuffer20100819Demo
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The main data elements of a class diagram are ''class'', ''association'' and ''attribute''. These elements all visualize Event-B data items (carrier sets, constants or variables) in the Event-B model. Only a class can visualize a carrier set. The class diagram also visualizes the relationships between these data items and generates constraints (invariants and axioms as appropriate) as follows.
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|An example project with a completed Tasking Development and IL1 model (post IL1 translation, but before Event-B translation).
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* '''Class Supertype''' relationships between classes represent that the source is a sub-set of the target superset.  
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|-
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* '''Association''' relationships represent that the association data is a relation between instances of the source and target classes. Cardinality may be used to further constrain the relationship to be for example a function, injection or surjection.
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|Sharedbuffer20100819Tasking
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* '''Attributes''' are similar to  associations except that the target is given by a text string (the attribute type property).
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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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|-
 
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|SharedBuffer20100819Tutorial
 
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|A bare project for step 1 of the tutorial.
 
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|-
 
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|Sharedbuffer20100819Tutorial2
 
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|A partially completed tasking development for steps 2 and 3 of the tutorial.
 
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|}
 
  
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== Preliminaries ==
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===Other Elements of a Class Diagram===
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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 .  
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* Constraints can be added to classes. The constraint is automatically universally quantified for all instances of the class. The user is expected to use the class' ''self name'' to represent the quantifier local variable. (By default the self name is ''this_<className>'' but it can be altered in the properties of the class). The constraint will generate an axiom or an invariant depending on wheter the class diagram is owned by a context or machine.
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==== The PrettyPrint View of a Tasking Development ====
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* For class diagrams that are owned by a machine, methods may be placed in classes. Methods are linked to events of the machine and a parameter is generated to represent the contextual instance, using the class' self-name. The user is expected to use the self name in guards and actions of the method. Note that the method-event elaborates relationship is many to many. Hence several methods in different classes could elaborate the same event. Conversely the same method may contribute its behaviour to several different events.
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To open the Tasking PrettyPrint viewer,
 
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* from the top-menu select ''Window/Show View/Other/Tasking Pretty Printer''.
 
  
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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.
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===Scope===
 +
Elements of the class diagram can define data in the containing Event-B component and can visualize data in any Event-B component that is visible to the containing Event-B component (including itself). Hence a class diagram in a context may visualize sets and constants in the containing context and visualize sets and constants in any context which is (transitively) extended by the containing context. A class diagram in a machine may define/visualize variables in the containing machine, visualize variables in any machine it (transitively) refines and visualize sets and constants in any context that is seen by the machine or any Context that is (transitively) extended by a context that is seen by the machine.
  
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* Open the ''SharedBuffer20100819Demo'' Project and switch to the Resource Perspective.
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===Secondary information===
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* Open the ''.tasking'' model and inspect it. Clicking on the Main, Machine or Event nodes updates the pretty print window.
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Colour is used to indicate whether a diagram element has been linked to data. Icons are used to indicate the kind (set, constant or variable) of elaborated data.
  
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==== Viewing Source Code ====
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==Examples==
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aka. The PrettyPrint View of an IL1 Model.
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For example when a class diagram is first drawn and has not been linked to data it looks like this:
  
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To view Ada source code,
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[[File:Cd1_unlinked.png]]
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* from the top-menu select ''Window/Show View/Other/IL1 Pretty Printer''.
 
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* Open the ''SharedBuffer20100819Demo'' Project and switch to the Resource Perspective.
 
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* Open the ''.il1'' model and inspect it. Clicking on the Protected, Main Entry, or Task nodes updates the pretty print window.
 
  
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==== Cleaning the Tasking Development ====
 
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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.
 
  
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== The Tutorial ==
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Generating this diagram produces no output to the Event-B.
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The steps needed to generate code from an Event-B model, in this tutorial, are as follows,
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The diagram elements must first be linked to data using the '''Link Data''' or '''Create & Link''' buttons in the properties sheet.
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* Step 1 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Creating_The_Tasking_Development Create the tasking development].
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The followng screenshot shows the association being linked to a variable ''b'' that already exists in the machine.
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* Step 2 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Providing_the_Annotations_for_Implementations Add annotations]
 
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* Step 3 - [http://wiki.event-b.org/index.php/Code_Generation_Tutorial#Invoking_the_Translation Invoke translators].
 
  
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==== Creating The Tasking Development ====
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[[File:LinkData.png|800px]]
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* Change to the Event-B Perspective.
 
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* Open the ''SharedBuffer20100819Tutorial'' Project.
 
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* Select the following Machines: Reader, Writer and Shared.
 
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* Right-click and select ''Make Tasking Development/Generate Tasking Development''.
 
  
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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.
 
  
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Change to the Project ''SharedBuffer20100819Tutorial2'' to begin the next step.
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The following screenshot shows the class A being used to create and link to a carrier set in the seen context X0. Note that the carrier set is created in X0 immediately. It is not necessary to generate.
  
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==== Providing the Annotations for Implementations ====
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[[File:CreatLink.png|800px]]
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* Close any Tasking Pretty Print Viewers that remain open. The incomplete model will give rise to exceptions.
 
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* Go to the to the Resource Perspective.
 
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* Open and inspect the ''.tasking'' machine.
 
  
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The ''WriterTsk'' and ''SharedObj'' machines are incomplete. We will take the steps to necessary to provide implementation details.
 
  
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===== The WriterTsk Machine =====
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After linking these diagram elements they are automatically rendered differently including icons for variables (b) and sets (A). Generating at this stage introduces an invariant for the association variable b to say that it is a relation between A and B. Since B only exists in the diagram and is not yet linked to any data, this causes an error in the machine. However, note that the invariant is still generated using the class name, B. In fact we could replace the class name with any valid expression (e.g. NAT) representing a set of instances.
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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.
 
  
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*'''Add Synchronisation between TWrite and SWrite'''.
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[[File:ClassDiagGen.png|800px]]
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** Expand the ''Auto Task Machine'' node.
 
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** Expand the ''Seq'' sub-tree.
 
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** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
 
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** Provide the event label ''w1'' using the properties view.
 
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** Right-click on Event Wrapper and select ''New Child/ Synch Events''.
 
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** Select ''Synch Events'' and go to the drop-down menu of the ''Local Event'' property.
 
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** At this point the drop-down box displays a number of event names, select the ''TWrite'' event.
 
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** Go to the drop-down menu of the ''Remote Event'' property.
 
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** From the list of events select the ''SWrite'' event.
 
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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.
 
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*'''Add the Wrapped Event TcalcWVal'''.
 
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** Expand the sub-tree of the second ''Seq'' node.
 
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** Right-click on the ''Seq'' node and select ''New Child/Left Branch EventWrapper''.
 
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** Provide the event label ''w2'' using the properties view.
 
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** Right-click on Event Wrapper and select ''New Child/ Synch Events''.
 
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** Select ''Synch Events'' and go to the drop-down menu of the ''Local Event'' property.
 
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** From the list of events select the ''TcalcWVal'' event.
 
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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''.
 
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*'''Add Event Extensions'''.
 
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** Right-click on the ''TWrite'' Event node.
 
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** Select ''New Child/Extension''.
 
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** Right-click on the ''Extension'' node and select ''New Child/Implementation'' from the menu.
 
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** Go to the Implementation properties view and set the ''Implementation Type'' property to ''ProcedureSynch''.
 
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*'''Identify Incoming and Outgoing parameters'''.
 
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** Right-click on the ''outAP'' node and add an ''Extension''.
 
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** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
 
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** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualOut''.
 
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** Right-click on the ''inAP'' node and add an ''Extension''.
 
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** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
 
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** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''actualIn''.
 
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===== The Shared Machine =====
 
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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.
 
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* Right-click on the ''SharedObj'' Machine node in the ''.tasking'' file.
 
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* Select ''New Child/Extension''.
 
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* Right-click on the ''Extension'' node and select ''New Child/Shared Machine'' from the menu.
 
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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''.
 
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* '''Identify SWrite as a Syncronisation'''.
 
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** Right-click on the ''SWrite'' Event node.
 
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** Select ''New Child/Extension''.
 
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** Right-click on the ''Extension'' node and select ''New Child/Implementation'' from the menu.
 
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** Go to the Implementation properties view and set the ''Implementation Type'' property to ''ProcedureSynch''.
 
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* '''Identify incoming and outgoing parameters'''.
 
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** Right-click on the ''inFP'' node and add an ''Extension''.
 
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** Right-click on the ''Extension'' and select''New Child/Parameter Type''.
 
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** Go to the ''Parameter Type'' properties view and set the ''Parameter Type'' property to ''formalIn''.
 
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** Right-click on the ''outFP'' node and add an ''Extension''.
 
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** 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''.
 
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===== A Summary of Steps =====
 
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For a Tasking Machine definition:
 
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# Add the Tasking Machine type (Auto etc).
 
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# Add the task type (Periodic etc.).
 
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# Define the task priority.
 
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# Define the task body.
 
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# For each event, add the Event Type.
 
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# For each event parameter, add the Parameter Type.
 
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−
 
 
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For a Shared Machine definition:
 
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# Add the ''SharedMachine'' Machine type.
 
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# For each event, define the Event Type.
 
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# For each event parameter, define the Parameter Type.
 
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==== Invoking the Translation ====
 

Revision as of 14:54, 5 October 2015

this page is under construction

IUMLB big.png

Introduction

In iUML-B, Class diagrams are used to define and visualize entity-relationship data models. They can be added to Event-B Machines and Event-B Contexts and visualize given sets , constants and variables. Diagram elements elaborate pre-existing user data in order to visualize it. The diagram defines type, sub-type and further constraint information for the data by generating invariants or axioms.

Principles of Operation

Classes, Attributes and Associations are all model elements that represent data. They can be linked to existing Event-B data elements: Variables, Constants or (for Classes only) Carrier Sets. This relationship is called Elaborates because the diagram element elaborates properties of the data item. Any data element within scope, locally within the same machine or context, or via sees and extends, can be elaborated. As a short cut, a button is provided to create a new data item and link to it in one step.

Class diagrams can be added to Machines or Contexts, but note that some features are not available when in a Context (e.g. only constants and sets are within scope to link to and methods cannot be used in classes).

Methods can be placed inside Classes and link (elaborate) one or more events in the containing Machine. This means that the elaborated events are given a paramter representing the class instance (similar to 'this' or 'self' in programming languages). When in variable classes (i.e. a class that elaborates a variable) methods may be constructors or destructors.

Main Data Elements of a Class Diagram

The main data elements of a class diagram are class, association and attribute. These elements all visualize Event-B data items (carrier sets, constants or variables) in the Event-B model. Only a class can visualize a carrier set. The class diagram also visualizes the relationships between these data items and generates constraints (invariants and axioms as appropriate) as follows.

  • Class Supertype relationships between classes represent that the source is a sub-set of the target superset.
  • Association relationships represent that the association data is a relation between instances of the source and target classes. Cardinality may be used to further constrain the relationship to be for example a function, injection or surjection.
  • Attributes are similar to associations except that the target is given by a text string (the attribute type property).

Other Elements of a Class Diagram

  • Constraints can be added to classes. The constraint is automatically universally quantified for all instances of the class. The user is expected to use the class' self name to represent the quantifier local variable. (By default the self name is this_<className> but it can be altered in the properties of the class). The constraint will generate an axiom or an invariant depending on wheter the class diagram is owned by a context or machine.
  • For class diagrams that are owned by a machine, methods may be placed in classes. Methods are linked to events of the machine and a parameter is generated to represent the contextual instance, using the class' self-name. The user is expected to use the self name in guards and actions of the method. Note that the method-event elaborates relationship is many to many. Hence several methods in different classes could elaborate the same event. Conversely the same method may contribute its behaviour to several different events.

Scope

Elements of the class diagram can define data in the containing Event-B component and can visualize data in any Event-B component that is visible to the containing Event-B component (including itself). Hence a class diagram in a context may visualize sets and constants in the containing context and visualize sets and constants in any context which is (transitively) extended by the containing context. A class diagram in a machine may define/visualize variables in the containing machine, visualize variables in any machine it (transitively) refines and visualize sets and constants in any context that is seen by the machine or any Context that is (transitively) extended by a context that is seen by the machine.

Secondary information

Colour is used to indicate whether a diagram element has been linked to data. Icons are used to indicate the kind (set, constant or variable) of elaborated data.

Examples

For example when a class diagram is first drawn and has not been linked to data it looks like this:

Cd1 unlinked.png


Generating this diagram produces no output to the Event-B. The diagram elements must first be linked to data using the Link Data or Create & Link buttons in the properties sheet. The followng screenshot shows the association being linked to a variable b that already exists in the machine.

LinkData.png


The following screenshot shows the class A being used to create and link to a carrier set in the seen context X0. Note that the carrier set is created in X0 immediately. It is not necessary to generate.

CreatLink.png


After linking these diagram elements they are automatically rendered differently including icons for variables (b) and sets (A). Generating at this stage introduces an invariant for the association variable b to say that it is a relation between A and B. Since B only exists in the diagram and is not yet linked to any data, this causes an error in the machine. However, note that the invariant is still generated using the class name, B. In fact we could replace the class name with any valid expression (e.g. NAT) representing a set of instances.

ClassDiagGen.png

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