XPath Query Relaxation through Rewriting Rules

Abstract

Query relaxation is the process of weakening a query to a more general one, and it is frequently employed to support approximate query answering. In this paper, rewriting systems for a wide fragment of XPath are investigated, which accomplish query relaxation through the application of simple rewriting rules transforming navigational axes and node tests into relaxed ones. Specifically, a general yet simple form of rewriting rules is considered, which subsumes the forms adopted in several rewriting systems for approximate XPath query answering. The expressiveness of rewriting systems based on this form of rules is characterized in terms of their capability of transforming a query into every more general formulation. It is shown that traditional rewriting systems are not only incomplete w.r.t. containment, but also w.r.t. the stricter form known as containment by homomorphism. This limitation is overcome by defining a set R Ã of rewriting rules which are still of the same simple form of traditional ones, but are expressive enough to catch at least containment by homomorphism. Then, an algorithm is proposed which exploits R Ã to provide approximate answers of queries along with a measure of their approximation degree.Index Terms-XPath, query relaxation, approximate query answering, information systems.

A Structural XPath Query Expansion Approach Based on XML Schema in Publish Subscribe System

“…In the area of query optimization, XML retrieval gets lots of attention. Query Relaxation [6,7] was proposed. However, the result is a more general query which covers users' interest but also relaxes the constraint too much.…”

Adaptive query relaxation and top‐ k result sorting of fuzzy spatiotemporal data based on XML

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“…I G U R E 7 Execution time for data set sizes 1000, 5000, and 8000 [Color figure can be viewed at wileyonlinelibrary.com] F I U R E 6 Recall of three algorithms under different T sim [Color figure can be viewed at wileyonlinelibrary.com] F I G U R E 8 Memory consumption for data set sizes 1000, 5000, and 8000 [Color figure can be viewed at wileyonlinelibrary.com]5.2.3 | Results sorting experimentThis group of experiments aims to verify the effect of SPQRR algorithm. We use formula(6) to represent the accuracy of the top-10 results in the set. Precision ={top-10 results relevant results} 10 .…”