On the use of Graph Grammars for defining the Syntax of Graphical Languages

In order to implement graphical editors which allow both for structured and free editing, a parsing algorithm is needed which can analyze a diagram according to a graphical syntax, and derive the structure depicted. We propose to split this analysis in two phases. The rst phase reads the picture objects as they were drawn, determines the spatial relations between them, and stores the whole in a graph. The second phase of the analysis searches this graph for patterns which form constructs of the language under consideration, and generates an abstract syntax graph of the depicted structure. We investigate whether graph grammars are a suitable formalism to deene both graphs and to specify the translations between the two. The description of the translation would deene the graphical syntax of L; graph rewriting according to this description would implement the corresponding graphical parser which performs the second phase of the analysis.