This thesis presents the Graphical Description Language (GDL), a meta-language for the specification of the graphical syntax of the Unified Modeling Language, version 2.0 (UML).
Visual languages have properties that cannot be expressed in conventional meta-languages for textual languages. To address these properties, we need to take into account that the symbols of the language most likely does not adhere to a sequential ordering. We therefore need a meta-language with some functionality which is able to address the fact that the symbols of most visual languages have a more or less arbitrary spatial ordering in the plane. The contribution of this thesis is such a meta-language, applicable for UML 2.0.
We give an overview of existing research in the field of visual languages and give an analysis of the graphical syntax of UML to highlight the issues a meta-language has to address. We also give a specification of a subset of UML, called Tuml (Tiny UML), to illustrate use of the meta-language.
GDL uses the Z Notation as its formal basis. In addition, to address the unique properties of visual languages, we use concepts from topology, geographical information systems theory and previously defined visual language formalisms.