A generalized parser for 2-D languages

The authors present an extension of the Earley´s (1970) generalized parser to the case of two-dimensional languages. They describe two-dimensional (positional) grammars as generalizations of context-free string grammars. The technique used to extend the Earley´s algorithm is the same used for constructing a positional LR (pLR) parser. The main idea is to allow the parser to choose the next symbol to parse from a two-dimensional space