Activity Model: A Declarative Approach for Capturing Communication Behavior in Object-Oriented Databases
Ling Liu, Robert Meersman · Very Large Data Bases · 1992
Communication behaviour represents the dynamic evolution and the cooperation of a group of objects in accomplishing a task. It is an important feature in object-oriented systems. This paper introduces an activity model for the declarative specification of such communication behaviour, including the temporal ordering of message exchanges within the object communications, and the behavioural relationships between activity executions. We develop two formal mechanisms: activity specialization and activity aggregation for abstract implementation of object communication in order to allow expressing complex behaviour in terms of simpler behaviour. Activities are seen as patterns of object communications, which explicitly capture the behavioural dependencies among cooperating objects, and proved to be an effective aid for implementing communication behaviour. We use first-order temporal logic for specification of communication constraints, and argue that the activity model as such provides an adequate computational framework for object communications, and strikes a better balance between the object communication paradigm and the object classification paradigm.