GENGED: a generic graphical editor for visual languages based on algebraic graph grammars

GENGED is a generic graphical editor supporting the graphical definition of visual languages. Given an alphabet and rules of a specific visual language, GENGED generates a syntax-directed graphical editor for this language. GENGED, as well as each visual language defined using GENGED, is based on algebraic graph grammars. A sentence is given by a graphical structure consisting of a logical (abstract syntax) and a visual level (concrete syntax). Both levels are connected by layout operations. Visual language rules are defined by graph grammar rules. The underlying logical structure, however is hidden from the user but it is essential for a formal presentation and manipulation of graphical structures on both levels. The manipulations are performed by a graph transformation machine working on the logical level, whereas a graphical constraint solver manages the layout the user works with.