Difference between pages "D45 Prover Enhancement" and "Parallel Composition using Event-B"

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= Overview =
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[[User:Renato]] at [[Southampton]] is in charge of the [[Parallel Composition using Event-B]].
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* Two tasks concerned the prover performance from the core platform: the addition of rewriting and inference rules, and the addition of a mechanism to allow the customization and the parametrization or combination of tactics. While the addition of rewriting and inference rules has always been a regular task to enhance the Rodin integrated prover during DEPLOY lifetime, a new way to manage tactics has been implemented. In fact, the user is now able to define various types of tactics called 'profiles' which could be customized and parameterized tactics to discharge some specific proof obligations.
 
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* {{TODO}} An overview of the contribution about the ProB Disprover (Daniel Plagge, Jens Bendiposto)
 
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* The SMT Solvers plug-in allowing to use the SMT solvers within Rodin is an effective alternative to the Atelier-B provers, particularly when reasoning on linear arithmetic. {{TODO}} (Laurent Voisin, Yoann Guyot)
 
  
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= Motivations =
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Composition is the process by which it is possible to combine different sub-systems into a larger system. Known and studied in several areas, this has the advantage of reusability and combination of systems especially when it comes to distributed systems. While applying composition, properties must be maintained and proofs obligations need to be discharged in order for the final result to be considered valid. Our goal is to add this feature to the Rodin Platform (using Event-B notation) and study the concerns, properties, conditions, proof obligations, advantages and disadvantages when create/analysing system specifications. Since the composition maintains the monotonicity property of the systems, the sub-systems can be refined independently on a further stage, preserving composition properties.
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== New rewriting and inference rules ==
 
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In an Event-B development, more than 60% of the time is spent on proofs. It has been a continuous aim to increase the number of automatically discharged proof obligations (POs) by improving the capabilities of the integrated sequent prover through the addition of rewriting and inference rules. These rules were provided through tactics, or existing or newly created. These tactics were automatic, or manual, or sometimes both. Providing new proving rules, even if it sometimes does not increase directly the number of automatically discharged POs aims to help the user to interactively discharge them and spare his time.
 
  
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== Advanced Preferences for Auto-tactics ==
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[[Image:share_event_machine.jpeg]]
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{{TODO}} ''To be completed by Nicolas Beauger''
 
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Sometimes, the automatic proofs fail because the order of the applied tactics doesn't lead to the proof obligation discharge. Previously the ordering of tactics was lost at each change. Another issue is to have more than one possibility to combine the tactics. Indeed, various combinators called ''tacticals'' allow to combine tactics in a specific manner thus providing a sort of tactic arithmetic. The advanced preferences for auto-tactics solved this two issues.
 
  
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== Isabelle Plug-in ==
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[[Image:share_event_mach_comp1.jpeg]]
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{{TODO}} ''To be completed by Matthias Schmaltz''
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[[Image:share_event_machine_comp2.jpg]]
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== ProB Disprover ==
 
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{{TODO}} ''Daniel Plagge, Jens Bendiposto''
 
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== SMT Solver Integration ==
 
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{{TODO}} ''Laurent Voisin'' & ''Yoann Guyot''
 
  
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= Choices / Decisions =
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A machine '''''S''''' with events '''''e1, e2, e3''''' and '''''e4''''' and variables '''''v1, v2''''' and '''''v3''''' can be decomposed using event (de)-composition of event ''e2'' (as can be seen above). This would result in the machine '''''S1''''' and '''''S2''''' that have a partial part of the event ''e2'': machine ''S1'' has the part related to the variable ''v1'' (''e2''') and machine ''S2'' has the part related to the machine ''v2'' (''e2''<nowiki>''</nowiki>). Also some other events are separated (''e1'' and ''v1'' only exist on machine ''S1'' and events ''e3'' and ''e4'' with variable ''v3'' only exist on the machine ''S2'') as can be seen above.
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== New rewriting and inference rules ==
 
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{{TODO}} ''To be completed by Laurent Voisin''
 
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== Advanced Preferences for Auto-tactics ==
 
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{{TODO}} ''To be completed by Nicolas Beauger''
 
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Since Rodin 2.1, simple tactic profiles have been added. They allow to persiste and set specifically for some project various ordered ways to apply the basic tactics. Since Rodin 2.3, tacticals and parameterisation have been added to the profiles increasing even more the potential of such proving feature. The combinators allow for exemple to loop on a subset of tactics, including existing profiles, and the parameterisation allows for example to set a timeout on external provers such as AtelierB P1.
 
  
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== Isabelle Plug-in ==
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The composition is based on proposals for parallel composition in Event-B in the following paper: [http://deploy-eprints.ecs.soton.ac.uk/51/].
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{{TODO}} ''To be completed by Matthias Schmaltz''
 
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== ProB Disprover ==
 
−
{{TODO}} ''Daniel Plagge, Jens Bendiposto''
 
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== SMT Solver Integration ==
 
−
{{TODO}} ''Laurent Voisin'' & ''Yoann Guyot''
 
  
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= Available Documentation =
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A release of the composition plugin for Rodin 0.8.2 is available (email me:ras07r@ecs.soton.ac.uk).
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* {{TODO}} Links for New rewriting and inference rules
 
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* {{TODO}} Links for Advanced Preferences for Auto-tactics
 
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* {{TODO}} Links for Isabelle Plug-in
 
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* {{TODO}} Links for ProB Disprover
 
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* {{TODO}} Links for SMT Solver Integration
 
  
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= Status =
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A release for Rodin 0.9.2.1 is now available from the Rodin Main Update Site.
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== New rewriting and inference rules ==
 
−
{{TODO}} ''To be completed by Laurent Voisin''
 
−
== Advanced Preferences for Auto-tactics ==
 
−
{{TODO}} ''To be completed by Nicolas Beauger''
 
−
== Isabelle Plug-in ==
 
−
{{TODO}} ''To be completed by Matthias Schmaltz''
 
−
== ProB Disprover ==
 
−
{{TODO}} ''Daniel Plagge, Jens Bendiposto''
 
−
== SMT Solver Integration ==
 
−
{{TODO}} ''Laurent Voisin'' & ''Yoann Guyot''
 
  
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[[Category:D45 Deliverable]]
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1. To create a new composition file (bcp file), go to Toolbar (on top), New>>Other... Event-B>>Composition Machine. Then select the project (if not selected already) and filename (by default is cm.bcp).
 +
 
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2. Bcp files are visible on Event-B perspective(from Rodin 0.9). For Rodin 0.8.2, go to Resource or Java perspective to edit the file.
 +
 
 +
3. After editing the properties of the bcp file, you can generate a new bum file (machine), by using the green button on the toolbar (CM - symbol of machine) or by right clicling on the bcp file and choose the option :'Create Composed Machine'. You will have to introduce a name for the new machine and after that is just press 'OK'.
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 +
 
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'''
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==User Manual==
 +
'''
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The Shared Event Composition Plugin is divided in 6 sections:
 +
 
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* '''Refines''' : allows to define an abstract machine of this composed machine. It is a valid machine that exists on the project.
 +
* '''Includes''': to compose a model, it is necessary to define which sub-systems(machines) interact. The machines must be abstract (not refinements of other machines) and have to be valid. It is also possible to choose if the included machine invariant should be visible to the composed machine or not (for proof optimization).
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* '''Sees''': allows to add contexts to the composed machine. The contexts seen by the ''included machines'' are visible to the composed machine. So it is only allowed to see contexts that are not already seen by the composed machine.
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* '''Invariants''': allows the inclusion of invariant clauses to the composed file. The inclusion of more invariants (from the included machines) depends on the user’s choice on ''Includes''. The defined invariants on the composed machine are “joint” properties between the included machines (gluing invariants), so variables and contexts from all the included machines become part of the composed machine scope.
 +
*'''Variant''': since the composed machine can be a refinement of an abstract model, there is the possibility of introducing new events. In order to avoid divergence, variants are necessary for the new events.
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*'''Composes Events''': the interaction between systems only happens when the composed events are synchronised and ready to be executed. The systems can interact through shared parameters. It is possible to define the following properties for composes events:
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** Name: name of the composes event
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** Extended/Not Extended: in the composes machine refines an abstract machine and if there are events with the same name, the concrete event can extend the abstract one (from Rodin 0.9).
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** Convergence: event can be chosen from ''Ordinary'', ''Convergence'' or ''Anticipated''.
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Still under '''Composes Events''', there are more properties that characterise a composed event:
 +
* '''Refines''' : possibility to choose if the composes event it is a refinement of an abstract event
 +
* '''Combines Event''': selection of the events that shall be composed. First the machine (out from the included machine list) is chosen and after, which event is supposed to be combined. It is possible to have only one combined event.
 +
 
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The '''Combination of Events''' can be expressed as:
 +
* The parameters are listed in one single (composed) event. Parameters (from different events) with the same name will be merged (becoming only one parameter). This correspond to the shared event composition with message passing, where a parameter is passed from one event to other.
 +
* The guards from the different combined events are merged using conjuction. So this composed event will be available if all the guards are true.
 +
* the actions are also merged and executed in parallel.
 +
 
 +
Like mention above,a machine can be generated containing all the properties defined on the composed machine file. The generation of the new machine can be executed by using the green button on the toolbar (CM - symbol of machine) or by right clicling on the bcp file and choosing the option :''Create Composed Machine''. A name for the new machine have to be introduced (a name is suggested by default ) and by clicking 'OK' or 'Override', a new machine file is generated.
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[[Category:Parallel composition plugin]]
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[[Category:User documentation]]

Revision as of 08:59, 4 March 2009

User:Renato at Southampton is in charge of the Parallel Composition using Event-B.

Composition is the process by which it is possible to combine different sub-systems into a larger system. Known and studied in several areas, this has the advantage of reusability and combination of systems especially when it comes to distributed systems. While applying composition, properties must be maintained and proofs obligations need to be discharged in order for the final result to be considered valid. Our goal is to add this feature to the Rodin Platform (using Event-B notation) and study the concerns, properties, conditions, proof obligations, advantages and disadvantages when create/analysing system specifications. Since the composition maintains the monotonicity property of the systems, the sub-systems can be refined independently on a further stage, preserving composition properties.

Share event machine.jpeg

Share event mach comp1.jpeg Share event machine comp2.jpg

A machine S with events e1, e2, e3 and e4 and variables v1, v2 and v3 can be decomposed using event (de)-composition of event e2 (as can be seen above). This would result in the machine S1 and S2 that have a partial part of the event e2: machine S1 has the part related to the variable v1 (e2') and machine S2 has the part related to the machine v2 (e2''). Also some other events are separated (e1 and v1 only exist on machine S1 and events e3 and e4 with variable v3 only exist on the machine S2) as can be seen above.

The composition is based on proposals for parallel composition in Event-B in the following paper: [1].

A release of the composition plugin for Rodin 0.8.2 is available (email me:ras07r@ecs.soton.ac.uk).

A release for Rodin 0.9.2.1 is now available from the Rodin Main Update Site.

1. To create a new composition file (bcp file), go to Toolbar (on top), New>>Other... Event-B>>Composition Machine. Then select the project (if not selected already) and filename (by default is cm.bcp).

2. Bcp files are visible on Event-B perspective(from Rodin 0.9). For Rodin 0.8.2, go to Resource or Java perspective to edit the file.

3. After editing the properties of the bcp file, you can generate a new bum file (machine), by using the green button on the toolbar (CM - symbol of machine) or by right clicling on the bcp file and choose the option :'Create Composed Machine'. You will have to introduce a name for the new machine and after that is just press 'OK'.


User Manual

The Shared Event Composition Plugin is divided in 6 sections:

  • Refines : allows to define an abstract machine of this composed machine. It is a valid machine that exists on the project.
  • Includes: to compose a model, it is necessary to define which sub-systems(machines) interact. The machines must be abstract (not refinements of other machines) and have to be valid. It is also possible to choose if the included machine invariant should be visible to the composed machine or not (for proof optimization).
  • Sees: allows to add contexts to the composed machine. The contexts seen by the included machines are visible to the composed machine. So it is only allowed to see contexts that are not already seen by the composed machine.
  • Invariants: allows the inclusion of invariant clauses to the composed file. The inclusion of more invariants (from the included machines) depends on the user’s choice on Includes. The defined invariants on the composed machine are “joint” properties between the included machines (gluing invariants), so variables and contexts from all the included machines become part of the composed machine scope.
  • Variant: since the composed machine can be a refinement of an abstract model, there is the possibility of introducing new events. In order to avoid divergence, variants are necessary for the new events.
  • Composes Events: the interaction between systems only happens when the composed events are synchronised and ready to be executed. The systems can interact through shared parameters. It is possible to define the following properties for composes events:
    • Name: name of the composes event
    • Extended/Not Extended: in the composes machine refines an abstract machine and if there are events with the same name, the concrete event can extend the abstract one (from Rodin 0.9).
    • Convergence: event can be chosen from Ordinary, Convergence or Anticipated.


Still under Composes Events, there are more properties that characterise a composed event:

  • Refines : possibility to choose if the composes event it is a refinement of an abstract event
  • Combines Event: selection of the events that shall be composed. First the machine (out from the included machine list) is chosen and after, which event is supposed to be combined. It is possible to have only one combined event.


The Combination of Events can be expressed as:

  • The parameters are listed in one single (composed) event. Parameters (from different events) with the same name will be merged (becoming only one parameter). This correspond to the shared event composition with message passing, where a parameter is passed from one event to other.
  • The guards from the different combined events are merged using conjuction. So this composed event will be available if all the guards are true.
  • the actions are also merged and executed in parallel.

Like mention above,a machine can be generated containing all the properties defined on the composed machine file. The generation of the new machine can be executed by using the green button on the toolbar (CM - symbol of machine) or by right clicling on the bcp file and choosing the option :Create Composed Machine. A name for the new machine have to be introduced (a name is suggested by default ) and by clicking 'OK' or 'Override', a new machine file is generated.

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