Improving the graph grammar parser of Rekers and Schurr

Graph grammars and graph grammar parsers are to visual languages what string grammars and parsers are to textual languages. A graph grammar specifies a set of valid graphs and can thus be used to formalise the syntax of a visual language. A graph grammar parser is a tool for recognising valid programs in such a formally defined visual language. A parser for context-sensitive graph grammars, which have proved to be suitable for formalising real-world visual languages, was developed by Rekers and Schürr. We propose three improvements of this parser. One of them enlarges the class of parsable graph grammars, while the other two increase the parser̈s computational efficiency. Experimental results show that for some (meaningful) graph grammars, our improvements can enhance the parser̈s performance by orders of magnitude. The proposed improvements will hopefully increase both the parser̈s applicability and the interest in visual language parsing in general.