On the minimization of Xpath queries

A Rewrite Approach for Pattern Containment

“…This grammar produces precisely the patterns as defined in [7,1]. For instance, the graph P in Figure 8 corresponds to the expression…”

“…The query equivalence problem is closely linked to the query minimization problem, which is essential for data base researchers. Since the time required for the evaluation of a given query Q is linear with respect to the size of Q ( [6]), the minimization -possibility of replacing Q by an equivalent query of smaller size -is of interest from the point of view of complexity ( [7,8,9,10]). …”

Cost-based Query Optimization for Xpath

“…At the logical level, the XML query optimization is to utilize the XML Schema, and to apply the rules of normalization or simplification to the inner query expressions so as to simplify the expressions that can improve the query performance. Lots of researches focusing on logical optimization have been done [3,4,5,6,7,9,10]. Our work focuses on the cost-based query optimization at the physical level and deals with how to determine the join order in query trees according to the cost estimation.…”

Efficient Processing of Multiple XML Twig Queries

“…-The set of nodes in the super twig pattern equals the union of the sets of nodes of all individual twig queries; -Each twig query is a subpattern (defined by [10]) of the super twig pattern; -If the queries have different root nodes, we rewrite the queries whose root nodes are not the root of the XML document and add the document's root as the root node of the queries. Then the root node of the super twig pattern is same as the document's root; -Suppose n is a query node which appears in q i and q j , P i and P j are the paths from the root to n in q i and q j respectively, P i is same as P j and m is the parent node of n in these two queries.…”