SOFL (Structured-Object-based-Formal Language) is recently proposed to combine the advantagesof formal methods, structured methods and object-oriented methodology into one method for software development. SOFL integrates modeling techniques from VDM (for specifying system component state) and data flow diagrams with Petri nets (for specifying system behaviours and interaction). To support the standardisation and the tool support for SOFL, a formal semantics of the language is desirable. As SOFL is under further development, the semantic representation of current SOFL needs to be easily reused and extended. In this paper, an object-oriented approach is taken to specify the semantics of SOFL and this approach is proved to be effective in providing a modular and reusable semantic representation. Object modeling techniques, such as inheritance is used to illustrate the common and the differences between various SOFL graphical constructs; object containment is used to capture the acyclic ...