P. T. Wood. Minimising simple XPath expressions. In WebDB, pages 13--18, 2001.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....of rewrite rules for eliminating upward modalities, which is similar to some of our results in Section 5. However, 19] focuses on a single large XPath fragment, and their results do not apply to the smaller fragments considered here. Normal forms for one simple fragment of XPath are examined in [26]; for tree patterns, 1, 20] present algorithms for achieving minimization, which can be viewed as a certain normal form for tree patterns. The issue of axiomatizing expression equivalence has been investigated for a number of formalisms related to XPath: 21] shows that there can be no finite ....

P. Wood. Minimising simple XPath expressions. In WebDB, 2001.

....this algorithm checks nondeterministically in polynomial time whether there is a counter example conforming to d which matches all patterns in P but not q. The reasoning for the correctness is similar to the case of CheckP. We note that in the above theorem, 2) and (3) were also obtained by Wood [24]. When disjunction, or filter and wildcard come in to play, the complexity raises from p and conp to exptime. Theorem 9. 1. Containment testing for XP(DTD, is in exptime. 2. Containment testing for XP(DTD, is hard for exptime. 3. Containment testing for XP(DTD, ....

P. T. Wood. Minimising simple XPath expressions. WebDB informal proceedings, 2001.

No context found.

P.T. Wood. Minimising simple XPath expressions. In Proc. WebDB 2001.

....Q 1 contains Q 2 ; that is, for every XML tree t, whether the output of Q 1 on t contains the output of Q 2 on t. Since XPath query containment has many applications in XML querying, integration, transformation and active rule [2] environments, it has been the subject of much study recently [1, 7, 9, 10, 15, 16]. Most of the papers cited above have studied different fragments of XPath, denoted XP in [9] depending on which XPath constructs are included in the fragment. All these fragments include node tests, composition of location steps ( and predicates ( XP adds wildcards ( ....

....descendants from that position in the query; without the : searching would start from the root node. In fact, the XPath fragments we consider do not allow the second form of query. ut a g i Fig. 1. The tree pattern for the XPath query a= b[ i] g. Deciding containment for XP is in ptime [16], a result which follows from the ptime containment for acyclic conjunctive queries [20] as pointed out in [9] Containment for XP is also in ptime [1] However, as shown recently by Miklau and Suciu [9] when we extend the XPath fragment to XP containment becomes conp complete. We are ....

[Article contains additional citation context not shown here]

P. T. Wood. Minimising simple XPath expressions. In Proc. WebDB 2001: Fourth Int. Workshop on the Web and Databases, pages 13--18, 2001.

....view the DTD as an equivalence class of models, such that the document is valid with respect to all members of the class, then MDL encoding could be used to choose the preferred model. The techniques we present here are also inspired by work on using DTDs to optimise queries on XML repositories [Woo00, Woo01]. Constraints present in DTDs can be used to detect redundant subexpressions in queries. For example, assume that a DTD implies that every date element which has a day element as a child must also have month and year elements as children. Now a query (on a set of documents valid with respect to ....

Peter T. Wood. Minimising simple XPath expressions. In Proceedings WebDB

....repaired using rules in the language. Secondly, we wish to further develop and gauge the effectiveness of our analysis methods. Techniques such as incorporating additional information from document type definitions may help obtain more precise information on triggering and activation dependencies [31]. We also wish to investigate the use of these dependencies for carrying out optimisation of ECA rules. ....

P. T. Wood. Minimising simple XPath expressions. In Proc. WebDB

....to be definitely True or False. This optimisation would modify the candidateDocs function described in Section 2.2. iii) The individual expressions in the condition and action parts of rules can be optimised by using recent results on equivalence and minimisation of XPath XQuery expressions [7, 36]. Further optimisations are possible if documents are known to satisfy various constraints by conforming to a schema or document type definition [7, 21, 36] 17 (iv) More global optimisation of rule conditions and actions is possible by using abstract interpretation to predict possible ....

.... in the condition and action parts of rules can be optimised by using recent results on equivalence and minimisation of XPath XQuery expressions [7, 36] Further optimisations are possible if documents are known to satisfy various constraints by conforming to a schema or document type definition [7, 21, 36]. 17 (iv) More global optimisation of rule conditions and actions is possible by using abstract interpretation to predict possible sequences of rule actions that may execute from the current database state, and then producing a specialised version of the rule execution semantics for each ....

P.T. Wood. Minimising simple XPath expressions. In Proc. WebDB 2001: Fourth Int. Workshop on the Web and Databases (Santa Barbara, Calif., May 24--25), pages 13--18, 2001.

No context found.

P. T. Wood. Minimising simple XPath expressions. In WebDB, pages 13--18, 2001.

No context found.

P. T. Wood. Minimising simple XPath expressions. In WebDB, pages 13--18, 2001.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC