Models XP for Rewriting XPath Queries

Abstract

This paper defines XP models for classes of XPath queries stored in cache, as materialized views. After declaration of issue of the correspondence between the tree models used for classes of XPath queries stored in cache and the set of trees associated to a XML document, it follows the solutions for rewriting the XPath views by transformation of patterns of trees. Author's personal contribution consists in modelling the set of trees associated to XP queries, for a multitude of constraints of XPath expressions and description of functions of correspondence in XP{ /, //, *, [] } representation. Verification of possibility to return the result of a query using the views materialized in cache requires the analysis of compatibility of tree models associated to XPath queries and XPath views materialized in cache. Finding a morphism of XP models demonstrates the real possibility of rewriting the XP view. This paper describes a method for establishing a semantic cache of XPath views. Composition of queries using a semantic cache of XP views, assumes the existence of a query which, by composition with a view from cache, will return the result of query.

Query Optimization against XML Data

“…The description of a semantic cache with n XPath views can be the following [14]: (2) where a and b are XML elements of view, 1  i  n; j, k  1.…”