Explicit modeling of semantics associated with composite states in UML statecharts

Abstract

UML statecharts are used for describing dynamic aspects of system behavior. The work presented here extends a general Petri net-based methodology to support formal modeling of UML statecharts. The approach focuses on the specific task of generating explicit transition models associated with the hierarchical structure of statechart. We introduce a state-transition notation to serve as an intermediate model for conversion of UML statecharts, and in particular, the complexity of composite states, to other target specifications. By defining a process for deriving, from UML statecharts, a statetransition notation that can serve as an intermediate state machine model, we seek to deepen understanding of modeling practices and help bridge the gap between model development and model analysis. This work covers all of the primary issues associated with the hierarchical structure of composite states, including entry and exit transitions, transition priorities, history states, and event dispatching. Thus, the results provide an important step forward toward the goal of modeling increasingly complex semantics of UML statecharts.Keywords: Composite States, Petri Nets, Statecharts, State-transition Notation, UML IntroductionThe Object Management Group (OMG) adopted a new paradigm for software development called Model Driven Architecture (MDA) [Poo01] to recognize the fact that models are important artifacts of software development and they serve as a basis for systems as they evolve from requirements through implementation. In MDA, models are defined in the Unified Modeling Language (UML), which is a graphical language for visualizing, specifying, constructing, and documenting a software-intensive system [BJR99]. MDA raises the importance of addressing many primary issues in the current standard of UML.One of the issues, the semantics of UML, is the subject of active discussion and much research activity [Rum98]. UML is a semi-formal language, since some parts of it are specified formally, while other parts, 1 This material is based upon work supported by the U.S. Army Research Office under grant number DAAD19-01-1-1-0672, and the U.S. National Science Foundation under grant number CCR-9988168.2 for instance dynamic semantics, are defined informally [OMG01]. The lack of formal dynamic semantics for this language limits its capability for analyzing defined specifications. The need for a formal semantics for UML is motivated in the literature [BL+00,FE+98], and the pUML (precise UML) group has been created to achieve this goal [PUML]. A number of projects discuss formalizing UML by mapping the UML notation to an alternative notation to give the UML notation a precise semantics and achieve UML verification. This paper is concerned with one core component of UML -statechart diagrams [OMG03].Statechart diagrams are used for describing dynamic aspects of system behavior in the framework of UML. states, and event dispatching. This work defines an important step forward toward the goal of modeling increasingly complex seman...

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