Improving the Definition of UML

Abstract

The literature on formal semantics for UML is huge and growing rapidly. Most contributions open with a brief remark motivating the work, then quickly move on to the technical detail. How do we decide whether more rigorous semantics are needed? Do we currently have an adequate definition of the syntax? How do we evaluate proposals to improve the definition? We provide criteria by which these and other questions can be answered. The growing role of UML is examined. We compare formal language definition techniques with those currently used in the definition of UML. We study this definition for both its content and form, and conclude that improvements are required. Finally, we briefly survey the UML formalisation literature, applying our criteria to determine which of the existing approaches show the most potential. Many would argue that UML has no semantics [HR04,HS05], despite the numerous subheadings with that title in the documents which define the language [Obj06,Obj03,Obj05c,Obj05a]. Bran Selic [Sel04] counters these claims by collecting and summarising the scattered material on semantics from the main official document [Obj05c]. He also encourages theoreticians to study ways of making the semantics more precise. The only real disagreement here is over the usage of the word "semantics." This is the topic of Harel and Rumpe's excellent article [HR04], and their position is that "semantics" is a mathematical term: Regardless of the exposition's degree of formality, the semantic mapping M : L / / S must be a rigorously defined function from the language's syntax L to its semantic domain S. Needless to say, an adequate semantic mapping for the full UML does not exist.

The Formal Semantics of the Domain Specific Modeling Language for Multiagent Systems

“…For instance, the authors of [13] give a recent overview of existing approaches and evaluate them using previously developed criteria. One of the most prominent approaches is the UML 2 Semantics Project [14] that develops mathematically formalized semantics for UML.…”