Extending UML 1.5 for fuzzy conceptual modeling: An strictly additive approach MIGUEL-ANGEL SICILIA 1 , NIKOS MASTORAKIS 2 1 Computer Science Department University of Alcalá Ctra. Barcelona, km.33,6 – 28871 Alcalá de Henares (Madrid) SPAIN 2 Military Inst. of University Education Hellenic Naval Academy Department of Electrical and Computer Engineering Terma Hatzikyriakou, 18539, Piraeus GREECE Abstract: - The Unified Modeling Language (UML) has become a widespread notation for conceptual modeling, and it currently provides a number of extensibility mechanisms to tailor it to specialized modeling issues. Some extensions have been proposed to extend the UML for fuzzy modeling, but without explicitly considering strict additivity and semantic compatibility with the original specification. In this paper, an analysis of these two issues is provided, describing the type of extensions that can be integrated with the current specification without breaking its semantics. Concretely, some forms of strictly additive fuzzy classification, fuzzy association, fuzzy generalization and fuzzy attribute values are sketched. Key-Words: - Fuzzy Conceptual Modeling, Unified Modeling Language, Meta-modeling, fuzzy class, fuzzy association, fuzzy generalization, fuzzy attribute values. 1 Introduction The Unified Modeling Language (UML) [3] has become a widely accepted graphical notation for conceptual modeling, and a large number of Software Engineering and general-purpose modeling tools now provide support for it. The UML has evolved into an OMG standard 1 , and its current 1.5 version is now subject of a major 2.0 revision that would eventually be available in 2004. Nonetheless, despite the flexibility of the UML to be adapted to diverse specific usages (e.g. business modeling, data modeling, service description, etc.), the UML does not provide explicit means to deal with information imperfections like uncertainty and imprecision [10], which were somewhat addressed in previous conceptual notations like Entity-Relationship models [1], and that can be considered an important domain aspect [6]. This has lead to some previous attempts to 1 http://www.omg.org/uml extend the UML in several dimensions of fuzzy conceptual modeling [2, 7, 9]. But these proposed extensions did not deal with the issue of analyzing which extensions are possible to add without breaking in some way the original core semantics of the language, and therefore, without loosing compatibility with existing tools and systems supporting the UML. Such an analysis is required from the viewpoint that non-compliant extensions would likely not be easily introduced in standard UML tools, and they may also introduce inconsistencies in formal accounts of conceptual modeling. This paper provides an analysis of the extensions that can be added to the UML 1.5 version in a strictly additive manner, i.e. those extensions that: (a) can be expressed through the built-in UML extensibility mechanisms, and that (b) do not break the semantics of the original model specification.