Relation grammars and their application to multi-dimensional languages

Relation grammars are introduced as a powerful formalism for specifying the syntax of visual languages and, more generally, of multi-dimensional languages. Textual languages use only the implicit relation of sequential concatenation of symbols. The proposed extension relax this limitation and allows the introduction of any number of relations. By analogy with textual grammars, relation grammars make it easier to recognize the purpose of the lexical analysis phase and that of the syntactic one for parsing multi-dimensional structures.