A Pr/T-Net model for context-free language parsing

This paper presents a Context-Free Grammar-Predicate/Transition-Net (CFG-Pr/T-Net) model for the parsing of context-free language. The places are defined to represent the states of the parsing process. The conditions and actions carried by the transitions are defined such that non-terminal symbols being processed can be rewritten and the derivation can be made to grow. Data structures, as the personalities of the token, are defined such that the growing derivation can be stored in the token. An application example was examined and the result shows that the Pr/T-Net model can do syntactic parsing successfully. The CFG-Pr/T-Net overcomes the limitation of pushdown automata, which only judged whether a string belonged to a given context free language, but were not able to answer the question concerning syntactic structure.