Abstract:

One of the key issues of object-oriented modeling and design is
inheritance. It allows for the definition of subclasses that inherit 
features of some superclass. Inheritance is well defined for static 
properties of classes such as attributes and operations. However, there 
is no general agreement on the meaning of inheritance when considering the
dynamic behavior of objects, captured by their life cycles. This paper 
studies inheritance of behavior in the context of UML. This work is based 
on a theoretical framework which has been applied and tested in both a 
process-algebraic setting (ACP) and a Petri-net setting (WF-nets). In this 
framework, four inheritance rules are defined that can be used to 
construct subclasses from (super-)classes. These rules and corresponding
techniques and tools are applied to UML activity diagrams, UML statechart 
diagrams, and UML sequence diagrams. It turns out that the combination of 
blocking and hiding actions captures a number of important patterns for 
constructing behavioral subclasses, namely choice, sequential composition, 
parallel composition, and iteration. Both practical insights and a firm 
theoretical foundation show that our framework can be used as a 
stepping-stone for extending UML with inheritance of behavior.