An interpreter for diagrammatic languages based on SR grammars

The authors describe a general-purpose tool for the specification and interpretation of visual languages based on the formalism of SR grammars. The major components of the system are a structure analyzer and an interpretation module. The structure analyzer consists of a general diagrammatic editor and a lexical analyzer. The main task of the lexical analyzer is then the identification of the relationships among the visual tokens composing the diagram. The resulting SR sentence is passed over to the interpretation module. The interpretation system consists of a syntactic and a semantic analyzer which make use of a user-supplied SR grammar and an attribute SR grammar, respectively. The syntactic analysis of the SR sentence is accomplished by means of a polynomial time parsing algorithm that outputs a tree structure, called SR-tree, describing the generation of both the s-items and the r-items composing the sentence. Given the SR-tree of the visual sentence, its meaning is achieved by performing a semantic analysis process, according to the attribute SR grammar. As for string grammars, an attribute SR grammar is obtained by associating semantic rules with the productions of the underlying SR grammar