A Syntax Parser Based On The Case Dependency Grammar And Its Efficiency

Augumented transition network grammars (ATNGs) or augumented contextfree grammars are generally used in natural language processing systems. The advantages of ATNGs may be summarized as i) efficiency of representation, 2) perspicuity, 3) generative power, and the disadvantage of ATNGs is that it is difficult to get an efficient parsing algorithm becuase of the flexibility of their complicated additional functions. In this paper, the syntax of Japanese sentences , based on case dependency relations are stated first, and then we give an bottom-up and breadth-first parsing algoritbxnwhich parses input sentence using time O(n 3) and memory space O(n2), where n is the length of input sentence. Moreover, it is shown that this parser requires time O(n2), whenever each B-phrase in input sentence is unambiguous in its grammatical structure. Therefore, the efficiency of this parser is nearly equal to the Earley's parser which is the most efficient parsing method for general context-free grammars.