Michelle L. Crane

UML vs. classical vs. rhapsody statecharts: not all models are created equal

State machines, represented by statecharts or state machine diagrams, are an important formalism for behavioural modelling. According to the research literature, the most popular statechart formalisms appear to be Classical, UML, and that implemented by Rhapsody. These three formalisms seem to be very similar; however, there are several key syntactic and semantic differences. These differences are enough that a model written in one formalism could be ill-formed in another formalism. Worse, a model from one formalism might actually be well-formed in another, but be interpreted differently due to the semantic differences. This paper summarizes the results of an informal comparative study of these three formalisms with the help of several illustrative examples. We present a classification of the differences according to the nature of potential problems caused by each difference. In addition, for each difference we discuss how translation between formalisms can be achieved, if at all.

Towards a UML virtual machine: implementing an interpreter for UML 2 actions and activities

An interpreter for UML 2 actions and activities is presented. It is based on two novel features in UML 2: the three-layer semantics architecture and the new token offer semantics for activities, which is intended to generalize the token flow semantics of Petri nets. The interpreter offers an array of analysis capabilities, ranging from random execution to reachability properties and assertion and deadlock checking. The design of the interpreter makes it suitable as the basis for a more comprehensive UML virtual machine.

2nd UML 2 semantics symposium: formal semantics for UML

The purpose of this symposium, held in conjunction with MoDELS 2006, was to present the current state of research of the UML 2 Semantics Project. Equally important to receiving feedback from an audience of experts was the opportunity to invite researchers in the field to discuss their own work related to a formal semantics for the Unified Modeling Language. This symposium is a follow-on to our first workshop, held in conjunction with ECMDA 2005.

Runtime Conformance Checking of Objects Using Alloy

Abstract Object models are an important part of most object-oriented software development methodologies, where they play a central role during the specification and design phases. However, their usefulness is much more limited during the implementation phase. In this paper, we demonstrate how confidence in source code can be increased by using runtime conformance checking to analyze the code with respect to an object model. More precisely, we use the Alloy Analyzer, developed at MIT, to determine automatically whether the runtime state of a program at certain user-specified locations conforms to a given object model. The design, implementation and evaluation of a prototype runtime conformance checker for Java programs with respect to Alloy object models is described.