UML with meaning

Abstract

To most in the software community, "modeling" is drawing pictures, something much different than "coding". While programming languages must be specified precisely enough to be executable, this has not necessarily been the case for modeling languages. Indeed, the well-known Unified Modeling Language (UML) has for years had a specification that is far from precise. However, precise models are quite common in other engineering disciplines, and there has been a minority even in software engineering that have created models that are precise enough to be, themselves, executable. Over the last decade, the UML community has more generally come to realize the benefits of having at least a subset of UML specified with precise execution semantics. While not all models need to be executable, executable models can support early testing and analysis of the design of critical software systems, as well as supporting simulation for communities using UML for modeling beyond just software (such as SysML for systems engineering). As a result, there has been a great deal of work in recent years toward the standardization of precise, executable semantics for UML models - the "meaning" behind the pictures: Foundational UML (fUML), the Action Language for fUML (Alf) and the recently completed Precise Semantics for UML Composite Structures. These new specifications provide the promise of widespread support for executable modeling across the many UML tools now on the market.