Implementation of a principle-based parser : based on On-Line Locality Principle

In this paper I present a principle-based parser based on Pritchett's theory of human sentence processing. The parser proceeds bottom-up and at each step it attempts to maximally satisfy the principles of the grammar; specifically, the parser satisfies the maximal number of theta and case requirements. This strategy does not guarantee that the best local choice will be the best choice globally; therefore the parser is obliged to backtrack. The reanalysis process is constrained by the On-Line Locality Principle, which is responsible for the selection of the solution in points of ambiguity. As a consequence the On-Line Locality Principle is responsible for failures of the revision process in the sense that the revision process may fail to recognize the grammatical structure of some sentences because of this constraint. The theory underlying the implementation guarantees that the revision process fails with all and only garden path sentences. When the failure of the revision process is caused by the On-Line Locality Principle the parser attempts to build a different structure that violates the On-Line Locality Principle, but nevertheless satisfies the grammar. If such a structure is found, then the sentence is potentially a garden path and an appropriate message is given. With an extension of the revision process to NP-traces, some island violations can be seen as a side effect of the parsing process. Following this idea, island violations are a special kind of garden path involving traces instead of open NPs.