VIATRA/Transformation/Transformation API

VIATRA2 EMF Transformation API

• Based on EVM
• Relies on Xtend features such as extension methods and closures to be
• Language concepts (for requirements overview)
• Documentation for API in org.eclipse.viatra2.emf.git (browse, stats, fork on OrionHub)

Batch Transformation API

Three extension classes used for transformations:

• BatchTransformation - hides IncQueryEngine and RuleEngine; manages group initialization of rules - instead of an extension method, this can also be used as a base class
• TransformationStatements - control structure
• ModelManipulation - generic model manipulation primitives; hides details of EditingDomains (if necessary); implementation not batch transformation specific

Batch Transformation Rules

• Special rule type
  • Precondition + action
  • Life cycle:
    • Stateless
      • rule does not maintain state whether an activation has fired or not
      • Lifecycle: firing: active -> active
    • Stateful
      • rule maintains whether an an activation has fired or not
      • Lifecycle: firing: active -> fired

(Batch) Transformation Statements

Name	Parameters	Description
choose	Batch Transformation Rule, (opt: filter)	Fires a single activation
forall	Batch Transformation Rule, (opt: filter)	Fires all current activations. If the firings change the set of activations, it won't change the set of fired activations.
until	Batch Transformation Rule, break condition, (opt: filter)	After firing the first activation, it checks whether the break condition became true; if yes, exits, if not, it restarts. It does not store the initial set of activations. Useful for iterate-choose scenarios. Break conditions are implemented using Match Predicates - functions that receive Match instances as parameters.
find	IQuerySpecification, (opt: filter)	Returns a match of a selected query

Incremental Transformation API

TBA

Model Manipulation Primitives

Model manipulation primitives are implemented by instances of IModelManipulations interface. Currently, two implementations are available:

1. SimpleModelManipulations - uses plain EMF API
2. ModelManipulationsWithEditingDomain - uses EMF Edit commands on EditingDomain instances

If some transformation needs specific primitives (e.g. transaction support), new instances can introduce extra methods as required.

Name	Parameters	Description
create	Resource; EClass	Creates an object with the corresponding EClass type, and puts it into the root of the selected resource
createChild	EObject (container); EReference; EClass	Creates an object with the corresponding EClass type, and puts it into the selected reference; the reference must be of containment type
addTo	EObject (container); EStructuralFeature; Object	Adds an existing object to the corresponding container with a reference; if using a reference it must *not* be of containment type
remove	EObject	Removes the EObject from the model
remove	EObject (container); EStructuralFeature; Object	Removes an object from the selected container; when using a containment EReference, also removes it from the resource set
remove	EObject (container); EStructuralFeature	Removes all objects from a multivalued feature; when using a containment EReference, also removes them from the resource set
set	EObject (container); EStructuralFeature; Object	Sets the value of a single-valued feature
move	EObject(s), EObject (new container), EStructuralFeature	Moves elements to a new container, and removes them from an old one. 'Remark': The implementation here is specific, as it relies on features of the index.

Examples

A (not very well tested) example transformation is available by implementing the Petri net to State Charts case of the Transformation Tool Contest 2013.

• Case description: http://planet-sl.org/community/index.php?option=com_community&view=groups&task=viewgroup&groupid=26&Itemid=387&lang=en
• Implementation: https://github.com/izsob/TTC13-PN2SC-EIQ (look for the branch viatra-api)