Subset and union properties in modeling languages

This paper discusses the new property characteristics in the Meta Object Facil-ity 2.0, namely subset and union properties. They are heavily used in the Unified Modeling Language 2.0 standard, but lack a formal definition. We give our un-derstanding of the new characteristics by formalizing subsets and unions using substitutability as our criterion. We present basic operations to create and edit models that use subset and unions properties. These operations form the basis of a model repository component in a modeling tool and are required to support Unified Modeling Language 2.0 models