Process Grammar Processor: an Architecture for a Parallel Parser
نویسنده
چکیده
A parallel architecture of a parser for Natural Language is described. A serial architecture has been already realized 6] and is currently used in the Process Grammar Development Environment (PGDE) 8], a system for the construction and testing of Natural Language grammars and the generation of the corresponding parsers. The PGDE is built around the Process Grammar Processor (PGP) running a model of grammar suited for the generation of Natural Language applications. The grammar model, named Process Grammar (PG), is an extension of an augmented context-free phrase-structure grammar, and the parser is designed to use such a grammar model. A PG is a set of rules that are treated by the processor as static descriptors of dynamic processes that are scheduled and applied if the conditions for their execution hold: from this the name Process Grammar. In this report the PG model is extended in order to allow a more structured and modular construction of grammars, even of big dimensions, keeping separated parsing control, and syntactic and semantic spec-iications, partitioning a PG in clusters of rules, completely independent one from each other, carrying on their own dedicated recognition of speciic parts of speech. The main steps of the serial PGP are realized in the parallel architecture as parallel processes that communicate between them the results of their computations using a message passing protocol. This allows the realization of some interesting parsing strategies and the implementation of parsing mechanisms extending the recognition capacity of the parser, e.g., it is possible to recognize context-sensitive grammars by means of a context-free device, and it is possible to perform more complex recognition steps that could not be possible in a serial and standard context-free parsing environment. Both serial and parallel versions of the parser are introduced and described, looking in greater detail the mechanisms of process scheduling, and how they can be used and extended for implementing various cases of parsing strategies.
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