Event-B Indexers

Purpose

Event-B indexers populate the index repository. Currently, indexers are implemented for the following files :

• machine (.bum)
• context (.buc)

Event-B Occurrence Kinds

So far, the following occurrence kinds have been defined :

• DECLARATION : when a variable, a carrier set, ..., is declared
• REFERENCE : when a variable, ..., is referenced (but not modified); also applies when an abstract element is redeclared in a refinement
• MODIFICATION : when a variable is modified

Please notice the distinction between the index repository notion of declaration (IDeclaration) and the Event-B occurrence kind DECLARATION.

What Indexers Index

Currently, indexed elements are :

• carrier sets
• constants
• variables
• events
• parameters

Formulas which cannot be parsed are ignored.

In the descriptions below, the following notation will be used to specify locations :

• [element] : internal location
• [element/attribute] : attribute location
• [element/attribute/begin..end] : attribute substring location

Context Indexer

Dependencies

• extended contexts

Declarations

• carrier sets
• constants

Occurrences

• DECLARATION of carrier sets [Root]
• DECLARATION of constants [Root]
• REFERENCE of elements in axioms [Axiom/Predicate/b..e]
• REFERENCE of elements in theorems [Theorem/Predicate/b..e]

Example:

 Ctx
 Sets
   S
 Constants
   C
 Axioms
   axm1 : C ∈ S

We will end up with the following occurrences :

 S :
   DECLARATION in [Ctx.Root]
   REFERENCE in [axm1/Predicate/4..5]
 C :
   DECLARATION in [Ctx.Root]
   REFERENCE in [axm1/Predicate/0..1]

Exports

• imported and declared carrier sets
• imported and declared constants

Machine Indexer

Dependencies

• refined machines
• seen contexts

Declarations

• variables
• events
• parameters

Occurrences

• DECLARATION of (local) variables [Root]
• DECLARATION of (local) events [Root]
• DECLARATION of (local) parameters [Event]
• REFERENCE of abstract variables in the local variables that redeclare them [Variable/Identifier]
• REFERENCE of abstract events in the local events that refine them [RefinesEvent/Target]
• REFERENCE of abstract parameters in the local parameters that redeclare them [Parameter/Identifier]
• REFERENCE of abstract parameters or variables in witnesses [Witness/Label]
• REFERENCE of elements in invariants [Invariant/Predicate/b..e]
• REFERENCE of elements in theorems [Theorem/Predicate/b..e]
• REFERENCE of elements in variants [Variant/Expression/b..e]
• REFERENCE of elements in guards [Guard/Predicate/b..e]
• REFERENCE of elements in witnesses [Witness/Predicate/b..e]
• REFERENCE of non assigned elements in actions [Action/Assignment/b..e]
• MODIFICATION of assigned elements in actions [Action/Assignment/b..e]

Example :

 M1
 VARIABLES
   var1
 INVARIANTS
   inv1 : var1 > 0
 EVENTS
   INITIALISATION
     THEN
       act1 : var1 := 1

After indexing M1, we will have the following occurrences:

 M1.var1 :
   DECLARATION in [M1.Root]
   REFERENCE in [M1.inv1/Predicate/0..4]
   MODIFICATION in [M1.act1/Assignment/0..4]
 M1.INITIALISATION :
   DECLARATION in [M1.Root]

Then, if we add another machine

 M2
 REFINES
   M1
 VARIABLES
   var1
 EVENTS
   INITIALISATION
     THEN
       act1 : var1 := 1

we will add the following occurrences :

 M1.var1 :
   REFERENCE in [M2.var1/Identifier]
 M2.var1 :
   DECLARATION in [M2.Root]
   MODIFICATION in [M2.act1/Assignment/0..4]
 M2.INITIALISATION :
   DECLARATION in [M2.Root]

Exports

• imported carrier sets
• imported constants
• local variables
• local events
• local parameters

Propagation

Propagators are defined for :

• events (EventPropagator) to propagate through refines
• parameters (IdentifierPropagator) to propagate through redeclaration
• variables (IdentifierPropagator as well) to propagate through redeclaration

In the above example with machines M1 and M2, after both files have been indexed, we can query occurrences of M1.var1.

With no propagator, the result would be :

 M1.var1 :
   DECLARATION in [M1.Root]
   REFERENCE in [M1.inv1/Predicate/0..4]
   MODIFICATION in [M1.act1/Assignment/0..4]
   REFERENCE in [M2.var1/Identifier]

Using the IdentifierPropagator, the result becomes :

 M1.var1 (propagated) :
   DECLARATION in [M1.Root]
   REFERENCE in [M1.inv1/Predicate/0..4]
   MODIFICATION in [M1.act1/Assignment/0..4]
   REFERENCE in [M2.var1/Identifier]
   DECLARATION in [M2.Root]
   MODIFICATION in [M2.act1/Assignment/0..4]

Query Examples

Here are a few examples of index queries. They are all implicitly preceded by the following code

 final IIndexQuery query = RodinCore.makeIndexQuery();
 query.waitUpToDate();

that makes the query and waits until the index becomes up-to-date.

Occurrences of an element

Data :

• a handle 'var' of an IVariable

To get its declaration

final IDeclaration declVar = query.getDeclaration(var);

Remember to check for a null return value.

From that declaration, the user-defined name of the variable can be retrieved

final String userDefinedName = declVar.getName();

To get the occurrences of 'var'

final Set<IOccurrence> occurrences = query.getOccurrences(declVar);

Homonyms in a file

Data :

• a handle 'file' of an IRodinFile
• a name "foo"

First, all declarations of all indexed elements that occur in 'file' are retrieved. Then a query filter on the name is used.

final Set<IDeclaration> declarations = query.getDeclarations(file);
query.filterName(declarations, "foo");

At the end, 'declarations' contains the declarations of all elements named "foo" occurring in 'file'.

Parameters of an event

Data :

• a handle 'file' of an IRodinFile
• a handle 'evt1' of an IEvent

Goal : getting the declarations of all parameters of 'evt1'

final Set<IDeclaration> declarations = query.getDeclarations(file);
query.filterType(declarations, IParameter.ELEMENT_TYPE);

final Set<IOccurrence> occurrences = query.getOccurrences(declarations);
query.filterKind(occurrences, EventBPlugin.DECLARATION);

final IInternalLocation evt1Location = RodinCore.getInternalLocation(evt1);
query.filterLocation(occurrences, evt1Location);

final Set<IDeclaration> paramsOfEvt1 = query.getDeclarations(occurrences);

We first get all declarations of elements that occur in 'file', and we filter them so as to keep only declarations of parameters.

We then get all occurrences of those parameters. We want parameters that have a DECLARATION occurrence in 'evt'. To that aim, two filters are successively applied to the occurrences.

Finally we get the declarations (IDeclaration) associated with the filtered occurrences.

Query with propagation

Data :

• a handle 'var' to a IVariable

Goal : getting all occurrences of 'var' including occurrences in machines that redeclare 'var'.

final IDeclaration declaration = query.getDeclaration(var);

final Set<IOccurrence> propagatedOccs = query.getOccurrences(declaration, EventBPlugin.getIdentifierPropagator());

Here, we start from the 'var' handle but of course, we could also have obtained its declaration by any other way (see other examples).

Returned occurrences can then be filtered, as usual.