Effective Guidance-Based XML Query Processing

XML queries are based on path expressions which are equal to a combination of some elements connected to each other in a tree pattern structure, called query tree pattern (QTP). The main operation in XML query processing is to find the nodes that match the given QTP in the document. A number of methods have offered for QTP matching; but the majority of these methods process all of the query nodes to access all QTPs in the document. A few methods such as TJFast process only nodes that satisfy leaves of QTP. All of above methods are trying to find a way just to optimizing direct comparing of nodes and to find the answer of query, directly via these comparisons. In this paper, we describe a novel method to find the answer of query without access to real data of the document blindly. In this method, first, the query will be executed on query guidance and this leads to a plan. Using this plan, it will be clear how to process leaf nodes and how to achieve query results, before processing of the document nodes. Therefore, none of document nodes will be processed blindly.