Difference between pages "D23 Flow Plug-in" and "D23 General Platform Maintenance"

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= Overview =
 
= Overview =
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{{TODO}}
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This first paragraph shall identify the involved partners and give an overview of the contribution. In particular, it shall provide answers to the following questions:
  
Event-B, being an event systems formalism, does not have a mechanism to explicitly define event ordering. Although event guards may express any desired event ordering, the ability to have a summary of possible event flows in a concise and compact form is useful for many tasks, for example, code generation and connecting with other formalisms. The flows plug-in addresses one aspect of event ordering: it allows a modeller to specify and prove that a given sequence of events does not contradict a given machine specification. More precisely, if we were to execute a machine step-by-step following our prescribed sequence of events we would not discover divergences and deadlocks not already present in the original machine. In other words, the constraint on event ordering must be such that the overall specification is an Event-B refinement of the original model. Importantly, this means that all the desired model properties proved before are preserved.
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*What are the common denominations?
 
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*Is it a new feature or an improvement?
Sequential composition of events may be expressed in a number of ways:
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*What is the main purpose?
* Event immediately follows another event; no other events may take place between the composed events.
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*Who was in charge?
* Event eventually follows an event; thus, although there is an interference from other events, it is guaranteed that the second is eventually enabled.
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*Who was involved?
* Event may follow an event; this is the weakest form of connection when we only say that it may be the case that the second event follows the first event; it may happen, however, that some other event interferes and the second event is delayed or is even not enabled ever.
 
 
 
Although the last case may seem the least appealing, it is the one that forms the basis of the Flows plug-in. The primary reason to offer such a weak guarantee is proof effort required for stronger types of connectives.
 
  
 
= Motivations =
 
= Motivations =
 
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{{TODO}}
There are a number of reasons to consider an extension of Event-B with an event ordering mechanism:
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This paragraph shall express the motivation for each tool extension and improvement. More precisely, it shall first indicate the state before the work, the encountered difficulties, and shall highlight the requirements (eg. those of industrial partners). Then, it shall summarize how these requirements are addressed and what are the main benefits.  
* For some problems the information about event ordering is an essential part of requirements; it comes as a natural expectation to be able to adequately reproduce these in a model.
 
* Explicit control flow may help in proving properties related to event ordering.
 
* Sequential code generation requires some form of control flow information.
 
* Since event ordering could restrict the non-determinism in event selection, model checking is likely to be more efficient for a composition of a machine with event ordering information.
 
* A potential for a visual presentation based on control flow information.
 
* Bridging the gap between high-level workflow and architectural languages, and Event-B.
 
 
 
It is also hoped that the plug-in would improve readability of larger models: currently they are simply a long list of events with nothing except comments to provide any structuring clues.  
 
  
 
= Choices / Decisions =
 
= Choices / Decisions =
 
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{{TODO}}
The primary functionality of the plug-in is the generation of additional proof obligations. Rodin model builder automatically invokes the static checker and the proof obligations generator of the plug-in and the proof obligations related to flow appear in the list of the model proof obligations.  
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This paragraph shall summarize the decisions (eg. design decisions) and justify them. Thus, it may present the studied solutions, through their main advantages and inconvenients, to legitimate the final choices.  
 
 
One of the lessons learned with an initial plug-in prototype was that a CSP-like language notation is not the best way to express event ordering as not all users are familiar with process algebraic notations. It was decided to use graphical editor to allow a visual layout of flow diagrams. This, in our view, is a more intuitive way of specifying event ordering. To realise this, we have relied on GMF - an Eclipse library to manipulate EMF models using graphical editors.
 
  
 
= Available Documentation =
 
= Available Documentation =
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{{TODO}}
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This paragraph shall give pointers to the available wiki pages or related publications. This documentation may contain:
  
There is a [http://wiki.event-b.org/index.php/Flows wiki] page summarising proof obligation involved in proving machine/flow consistency.
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*Requirements.  
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*Pre-studies (states of the art, proposals, discussions).  
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*Technical details (specifications).  
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*Teaching materials (tutorials).
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*User's guides.
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A distinction shall be made on the one hand between these different categories, and on the other hand between documentation written for developers and documentation written for end-users.  
  
 
= Planning =
 
= Planning =
The plug-in is available since the release 1.2 of the platform.
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{{TODO}}
 
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This paragraph shall give a timeline and current status (as of 29 Jan 2010).
[[Category:D23 Deliverable]]
 

Revision as of 13:43, 10 November 2009

Overview

TODO This first paragraph shall identify the involved partners and give an overview of the contribution. In particular, it shall provide answers to the following questions:

  • What are the common denominations?
  • Is it a new feature or an improvement?
  • What is the main purpose?
  • Who was in charge?
  • Who was involved?

Motivations

TODO This paragraph shall express the motivation for each tool extension and improvement. More precisely, it shall first indicate the state before the work, the encountered difficulties, and shall highlight the requirements (eg. those of industrial partners). Then, it shall summarize how these requirements are addressed and what are the main benefits.

Choices / Decisions

TODO This paragraph shall summarize the decisions (eg. design decisions) and justify them. Thus, it may present the studied solutions, through their main advantages and inconvenients, to legitimate the final choices.

Available Documentation

TODO This paragraph shall give pointers to the available wiki pages or related publications. This documentation may contain:

  • Requirements.
  • Pre-studies (states of the art, proposals, discussions).
  • Technical details (specifications).
  • Teaching materials (tutorials).
  • User's guides.

A distinction shall be made on the one hand between these different categories, and on the other hand between documentation written for developers and documentation written for end-users.

Planning

TODO This paragraph shall give a timeline and current status (as of 29 Jan 2010).