Open-World Loose Semantics of Class Diagrams as Basis for Semantic Differences

Abstract

Class Diagrams (CDs) model data structures in object-oriented systems and evolve throughout the course of the development process. Analyzing the semantic differences between consecutive versions of a CD is crucial to detect unintended changes of the modeled structures and involves comparing the sets of valid object models of both CDs. Established definitions of CD-semantics employ a closed-world assumption for the validity of object structures, which may not fit all stages of the development process. In this paper, we provide different definitions of CD-semantics and discuss their validity, relationship and limitations in the context of semantic evolution analysis. We show that the closed-world semantics of a CD is a subset of its open-world semantics and how this can be used for analyzing model-evolution. We also consider objects both as simple datastructures, as well as instances of (super-)classes and interfaces, and analyze how these approaches affect refinement and refactoring.