Automata-based Xpath Query Model

With applications of the XML data in the internet unceasing growth, the large XML data stream inquiry is becoming the hot spot in the data inquiry domain. The problem of XML data stream inquiry mainly sums up to the XPath inquiry, but how to effective processing XPath expression with predicate is the key question which of the XPath inquiry research needs to solve. Introduces the automata technology into the XPath inquiry domain to solve the difficult of predicate processing ,is one of important directions in present domestic and foreign research.This paper first research the automata technology in the XPath inquiry application, then propose an new model on AFA for evaluate XPaths with predicates:XBA. XBA rewrite the transfer function, fully use the characteristic of AFA can express and/or semantics to procese predicate, also,in XBA, a converse analyse method is used to construct transition function, to reduced the state number when XBA is runing. Experimental results show that XBA can improve the efficiency of evaluate XPaths with predicates.In the end of this paper , to resolve the low processing efficiency problem which be caused by the semantic identifier"//" and "*", propose an optimization technology based on the XML Schema, it determines the XPath expression using the XML Schema restraint. The theoretical analysis and the experimental results show that, after the optimized the XBA' s processing efficiency is higher than before the optimized.