In conceptual modeling, the universe of discourse (UoD) is divided into classes which have a taxonomic structure. The classes are usually defined in terms of attributes (all objects in a class share attribute names) and possibly of events. For enmple, the class of employees is the set of objects to which attributes like name, emp# etc. are applicable, and to which events li.Jce change -salary, change -address etc. are applicable. The events belong to the class because they change attributes applicable to objects in the class. We can add one more level of specification and define, for each class, a process composed of the events applicable to objects in that class. Thus, there is an employee process, consisting of events like change-salary etc. The problem is what the taxonomic strucrure of processes is. Attributes and eventc; are specialized if we descend in the taxonomic structure, i.e. a specialization in some sense has the "same" attributes and events as its generalizations, plus something extra which is definitive of this particular specialization. Conversely, ascending in the taxonomic structure corresponds to generalization. How are processes specialized and generalized? This report studies a particular formalization• of process generalization, based on abstraction in process algebra and uses this formalization to point out some fundamental problems with process generalization and specialization.
|Publisher||Vrije Universiteit, Department of Mathematics and Computer Science|