Reserved Graph Grammar: A Specification Tool for Diagrammatic VPLs

When implementing textual languages, formal grammars are commonly used to facilitate understanding languages and creating parsers. In the implementation of a diagrammatic visual programming language (VPL), this rarely happens, though graph grammars with their well– established theoretical background may be used as a natural and powerful syntax–definition formalism. Yet all graph grammar parsing algorithms presented up to now are either unable to recognize interesting visual languages or tend to be hopelessly inefficient (with exponential time complexity) when applied to graphs with a large number of nodes and edges. This paper presents a context–sensitive graph grammar called reserved graph grammar, which can explicitly, efficiently and completely describe the syntax of a wide range of diagrams using labeled graphs. Moreover, its parsing algorithm is of polynomial time complexity in most cases.