Decomposition and Composition of Sequence Diagrams

Abstract

As a semi-formal model, a UML sequence diagram can be widely useful for modelling and analyzing functional behaviors of a developing software system. However, reasoning about decomposition and composition of sequence diagrams has not been addressed adequately. The traditional decomposition method is based on the ideas from a global system to local components, and local components are recomposed into the whole system according to communication assumptions or other mechanisms. In this paper, we propose an event-based formal semantics for sequence diagrams and present a new functional decomposition approach based on sequence diagrams. The new decomposition idea is from a global system to global subsystems. Under the decomposition method global subsystems can be recomposed into the global system using the composition operation called union without necessarily considering assumptions such as communication.