Query Processing and Optimization for Regular Path Expressions

Abstract

Regular path expression is one of the core components of XML query languages, and several approaches to evaluating regular path expressions have been proposed. In this paper, a new path expression evaluation approach, extent join, is proposed to compute both parent-children (‘/’) and ancestor-descendent (‘//’) connectors between path steps. Furthermore, two path expression optimization rules, path-shortening and path-complementing, are proposed. The former reduces the number of joins by shortening the path while the latter optimizes the execution of a path by using an equivalent complementary path expression to compute the original path. Experimental results show that the algorithms proposed in this paper are much more efficient than conventional ones.KeywordsQuery ProcessingQuery OptimizationQuery PlanPath QueryPath ExpressionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.