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Connections to the UML Meta-model
As explained in the previous page, the MESSAGE meta-model extends the UML meta-model. That is:
- the MESSAGE meta-model by default includes all the concepts in the UML meta-model
- the additional concepts introduced in MESSAGE are defined relative to the UML concepts using the MOF meta-modelling language constructs (mainly specialisation)
Main specialisation linkages
All MESSAGE concepts are either MESSAGE-entities or MESSAGE-relationships.
- MESSAGE-entity specialises UML Classifier (it is possible this should be changed to UML Class, which is a specialisation of UML Classifier)
- MESSAGE-relationship specialises UML Relationship (which includes specialisations: Association, Dependency, Generalisation). More specific specialisation linkages are explained on a case-by-case basis.
Some of fundamental concepts in the MESSAGE Foundation package are very closely related to concepts in the UML Behavioural Elements package. They are essentially the same concepts, but the UML specification defines their meaning only in an object-oriented context. Consequently, the MESSAGE meta-model needs to re-define the semantics to enable them to be used as a foundation for the higher-level agent-oriented concepts. The OO and AO interpretations are consistent, however. The concepts in question are:
There is also a close relationship between:
However, Situation does not use the (optional) prescriptive dynamic aspects of UML State. Consequently it would be better to regard MESSAGE Situation and UML state as specialisation of a common ancestor. The same is true to a lesser extent of the two variants of Action and Event. If only the more abstract semantics of UML State are used, Situation can be regarded as a specialisation of UML State.
Other points of linkage
The following help link the lower-level aspects of agent behaviour with the UML Behavioural concepts.
- ConcreteEntity and Activity specialise UML StateMachine
- Task specialises UML ActionState, in the sense that a sub-task within a composite Task is an ActionState of the composite Task (which is a StateMachine).
- TemporalRelationhip (MESSAGE) specialises Transition (UML).
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Document maintained by: Paul Kearney, last updated 16th March 2001