Evaluation Techniques for Generalized Path Pattern Queries on XML Data

Wu, X; Theodoratos, D; Souldatos, S; Dalamagas, T; Sellis, T

dc.contributor.author	Wu, X	en
dc.contributor.author	Theodoratos, D	en
dc.contributor.author	Souldatos, S	en
dc.contributor.author	Dalamagas, T	en
dc.contributor.author	Sellis, T	en
dc.date.accessioned	2014-03-01T01:33:27Z
dc.date.available	2014-03-01T01:33:27Z
dc.date.issued	2010	en
dc.identifier.issn	1386-145X	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/20425
dc.subject	XML	en
dc.subject	XPath query evaluation	en
dc.subject.classification	Computer Science, Information Systems	en
dc.subject.classification	Computer Science, Software Engineering	en
dc.subject.other	Different structure	en
dc.subject.other	Evaluation models	en
dc.subject.other	Evaluation techniques	en
dc.subject.other	Experimental evaluation	en
dc.subject.other	Key operations	en
dc.subject.other	Partial specifications	en
dc.subject.other	Path queries	en
dc.subject.other	Pattern query	en
dc.subject.other	Querying of data	en
dc.subject.other	Spanning tree	en
dc.subject.other	Streaming model	en
dc.subject.other	Structural pattern	en
dc.subject.other	Structural summary	en
dc.subject.other	Topological ordering	en
dc.subject.other	Tree pattern	en
dc.subject.other	XML data	en
dc.subject.other	XML data sources	en
dc.subject.other	XML query processing	en
dc.subject.other	XPath query evaluation	en
dc.subject.other	Algorithms	en
dc.subject.other	Query languages	en
dc.subject.other	Topology	en
dc.subject.other	Trees (mathematics)	en
dc.subject.other	XML	en
dc.subject.other	Query processing	en
dc.title	Evaluation Techniques for Generalized Path Pattern Queries on XML Data	en
heal.type	journalArticle	en
heal.identifier.primary	10.1007/s11280-010-0092-2	en
heal.identifier.secondary	http://dx.doi.org/10.1007/s11280-010-0092-2	en
heal.language	English	en
heal.publicationDate	2010	en
heal.abstract	Finding the occurrences of structural patterns in XML data is a key operation in XML query processing. Existing algorithms for this operation focus almost exclusively on path patterns or tree patterns. Current applications of XML require querying of data whose structure is complex or is not fully known to the user, or integrating XML data sources with different structures. These applications have motivated recently the introduction of query languages that allow a partial specification of path patterns in a query. In this paper, we consider partial path queries, a generalization of path pattern queries, and we focus on their efficient evaluation under the indexed streaming evaluation model. Our approach explicitly deals with repeated labels (that is, multiple occurrences of the same label in a query). We show that partial path queries can be represented as rooted dags for which a topological ordering of the nodes exists. We present three algorithms for the efficient evaluation of these queries. The first one exploits a structural summary of data to generate a set of path patterns that together are equivalent to a partial path query. To evaluate these path patterns, we extend a previous algorithm for path-pattern queries so that it can work on path patterns with repeated labels. The second one extracts a spanning tree from the query dag, uses a stack-based algorithm to find the matches of the root-to-leaf paths in the tree, and merge-joins the matches to compute the answer. Finally, the third one exploits multiple pointers of stack entries and a topological ordering of the query dag to apply a stack-based holistic technique. We analyze our algorithms and perform extensive experimental evaluations. Our experimental results show that the holistic algorithm outperforms the other ones. Our approaches are the first ones to efficiently evaluate this class of queries in the indexed streaming model. © 2010 Springer Science+Business Media, LLC.	en
heal.publisher	SPRINGER	en
heal.journalName	World Wide Web	en
dc.identifier.doi	10.1007/s11280-010-0092-2	en
dc.identifier.isi	ISI:000281394200003	en
dc.identifier.volume	13	en
dc.identifier.issue	4	en
dc.identifier.spage	441	en
dc.identifier.epage	474	en