Formalizing UML 2.0 State Machines Using a Structure-Behavior Coalescence Method

UML State Machine Diagrams (SMDs) are a core component of the UML 2.0 specification for complex systems. These SMDs provide certain overview features to ordinary state machines, such as by providing orthogonal states and hierarchical nesting of subsystem SMDs. Despite these overview aspects, designing SMDs remains a relatively lower-level procedure. We propose to create a formal high-level overview diagram for SMDs, derived from the well-established rules of structure-behavior coalescence (SBC) process algebra. The proposed approach provides rules for transforming a low-level event transition graph (ETG) from a high-level ETG overview diagram (EOD). The smooth integration of a high-level representation with its precise low-level semantic meaning offers a new way to design and represent UML SMDs.