Refinement in object-oriented analysis and design

In this report refinement in object-oriented analysis and design is studied. We focus on process aspects of object-oriented designs, in particular protocols. Protocols describe the order of method invocations in a design. Process algebra is used to give semantics to protocols. Hence refinement in process algebra is studied in this report. There are two kinds of refinement in process algebra: ordinary refinement and action refinement. Ordinary refinement changes the structure of the system, not its actions. Several ordinary refinement relations are distinguished after their properties. The kind of action refinement we study is vertical refinement. A vertical refinement relation is defined on top of an ordinary refinement relation and has in addition a refinement function that maps every abstract action to a term of concrete actions. Advantage of vertical refinement is that abstract actions may be interleaved in the concrete system. Because vertical refinement abstracts from data, and this abstraction sometimes yields incorrect designs, read and write information is added to actions. With this information, serialisability of refinements is checked. The theory of vertical refinement is compared with the idea of refinement with transactions. Furthermore, the integration of ordinary refinements is studied. For the integration of vertical refinements, partial results are given. Finally, the theory is applied to object-oriented designs. Conclusion is that especially action refinement offers a great promise for the design of complex information systems. Furthermore, the formal definition of refinement makes a correct implementation in a tool possible.