Decomposition Plug-in User Guide: Difference between revisions

From Event-B
Jump to navigationJump to search
imported>Pascal
imported>Pascal
Line 105: Line 105:
[[Image:scenario2.png|center|500px|]]
[[Image:scenario2.png|center|500px|]]
</ol>
</ol>
== Release Notes ==
See the [http://wiki.event-b.org/index.php/Decomposition_Release_History Decomposition Release History].


[[Category:User documentation]]
[[Category:User documentation]]
[[Category:Work in progress]]
[[Category:Work in progress]]

Revision as of 15:19, 18 November 2009

Introduction

The Decomposition plug-in allows to decompose a model into sub-models.

See the Event-B Model Decomposition page for technical details on shared variables (A-style) decomposition.

Installing and Updating

Setup

The following steps will guide you through the setup process:

  1. Download Rodin for your platform from Sourceforge:
  2. Extract the downloaded zip file.
  3. Start Rodin from the folder where you extracted the zip file in the previous step.
  4. Install the Decomposition plug-in:
    1. In the menu choose Help -> Software Updates...
    2. Select the tab Available Software and click Add Site...
    3. Use the location URL: http://rodin-b-sharp.sourceforge.net/updates
    4. Back in Available Software open the update site you just added
    5. Select Event-B Decomposition and click Install...
  5. Restart Rodin as suggested.

Now you are ready to use the Decomposition plug-in.

Update

The following steps will guide you through the update process:

  1. In Rodin open the preferences (Window -> Preferences or for Mac: Rodin -> Preferences)
  2. Find Install/Update -> Automatic Updates
  3. Select Automatically find new updates and notify me

As soon as Rodin finds a new update it will ask you if you would like to install it.

Release Notes

See the Decomposition plug-in release history.

Decomposing

TODO

Selecting the Input Machine

Setting the Preferences

Decomposition style, decomposition of the contexts, etc.

Importing / Exporting the Configuration

Reporting a Bug or Requesting a Feature

Please, use the SourceForge trackers to report a bug on existing features, or to request new features:

Error Messages

When running the decomposition

The decomposition is forbidden, and an error message is displayed, if one of the following conditions applies:

  • The built INITIALISATION events of the sub-machines would define an action modifying at the same time a private variable and a shared variable.
Action {0} of the INITIALISATION event modifies a private variable and a shared variable
See Ensuring that a shared variable is not refined by an initialization event for further explanations.
  • The sub-models shall be created in new Event-B projects, but one of the entered project names already exists.
The project {0} should not exist
  • The same project name has been entered for two distinct sub-models.
Duplicate sub-model names: {0}

When running the static checker

The following rules are enforced by the static checker, and errors are returned (in the Rodin Problems view) accordingly:

  • A shared variable shall be present in subsequent refinements.
Shared variable {0} has disappeared
  • A shared variable shall still have the shared attribute in subsequent refinements.
Inconsistent nature of shared variable {0}, shared expected
  • An external event shall be present in subsequent refinements.
External event {0} has disappeared
  • An external event shall still have the external attribute in subsequent refinements.
Inconsistent status of external event {0}, external expected
  • An external event shall have the extended attribute in subsequent refinements.
Inconsistent status of external event {0}, extended expected
  • An external event shall not declare any additional parameter in subsequent refinements.
Parameters cannot be added in external events
  • An external event shall not declare any additional guard in subsequent refinements.
Guards cannot be added in external events
  • An external event shall not declare any additional action in subsequent refinements.
Actions cannot be added in external events
  • An INITIALISATION event shall not contain an action modifying at the same time a private variable and a shared variable.
Action {0} of the INITIALISATION event modifies a private variable and a shared variable
  • The actions of an INITIALISATION event modifying a shared variable shall be present and be syntactically equal in subsequent refinements.
Action {0} of the INITIALISATION event has disappeared

For additional information, see:

Tips and Tricks

Shared variables (A-style) decomposition

  1. An invariant is missing in a sub-machine, but I would like to have it copied.
    For example, an invariant between a concrete variable and some abstract variable may be useful.
    A solution is to add a theorem based on the missing predicate in the non-decomposed machine. See the last paragraph about the invariants in the Event-B Model Decomposition page.
  2. An axiom is missing in a sub-context, but I would like to have it copied.
    Such a situation may be encountered if the "Decompose contexts" option is checked.
    The workaround proposed for the invariants applies to the axioms as well.
    For example, if the non-decomposed context defines the axiom a \in S, and this axiom is not copied in a sub-context which contains the S carrier set but does not contain the a constant, then the information S \neq \emptyset is lost. In order to keep it, it is possible to add the theorem \exists x \qdot x \in S in the non-decomposed context.
  3. A variable is tagged as private in a sub-machine, but I would like to have it tagged shared.
    Such a behavior is suitable if you want to prevent this variable from being further refined.
    A solution for such a variable v of a sub-machine M_i is to add a fake action v \bcmeq v in a event of the non-decomposed machine which is associated to the sub-machine M_j (M_i and M_j are distinct sub-machines) when performing the decomposition.
    In the first example below, the min variable will become private when performing the decomposition:
    In the second example below, the min variable will become shared when performing the decomposition:

Release Notes

See the Decomposition Release History.