XML Query Languages. Content. Slide 1 Norbert Gövert. January 11, XML documents as trees. Slide 2. Overview on XML query languages XQL

Transcription

1 XML Query Languages Slide 1 Norbert Gövert January 11, 2001 Content Slide 2 XML documents as trees Overview on XML query languages XQL XIRQL: IR extension for XQL 1

2 XML documents as trees Slide 3 <book class="h.3.3" pubyear="2000"> <author>john Smith</author> <title>xml Retrieval</title> <chapter> <>Introduction</> This text explains all about XML and IR. </chapter> <chapter> <> XML Query Language XQL </> <section> <>Examples</> </section> <section> <>Syntax</> Now we describe the XQL syntax. </section> </chapter> </book> 2

3 XML documents as trees (2) pubyear="1999" book class="h.3.3" Slide 4 chapter chapter author title John Smith This... section section XML Retrieval Introduction XML Query Language XQL We describe syntax of XQL Examples Syntax 3

4 Overview on XML query languages Two views on XML documents document-centric data-centric Slide 5 XML query languages should support both views Selection of subtrees XQL, XPath Restructuring of result sets XML-QL, Quilt Information Retrieval XIRQL 4

5 XML-QL: Example Slide 6 CONSTRUCT <bib> { WHERE <bib> <book pubyear=$y> <title>$t</title> <author>john Smith</author> </book> </bib> IN "ls6- $y > 1991 CONSTRUCT <book year=$y><title>$t</title></book> } </bib> 5

6 XQL XML document as a tree (element nodes, attribute nodes, text nodes (content in leaf nodes) result of XQL queries is a set of nodes (subtrees) Examples: Slide 7 /book/chapter all chapter nodes which are children of the root element book //chapter all chapter nodes //chapter/ all s which are children of chapter nodes //chapter// descendants rather than children //chapter[] chapters which have a //chapter[ = "XML"] chapters with given 6

7 Examples (continued) XQL (2) //chapter/ = "XML" returns s rather than chapters /book[author = "Smith"]/chapter[ = "XML"] combination, returns chapters Slide 8 /book[author = "Smith" Boolean operators title = "Databases"] /book[.// = "XML"] use. to refer to current node /book[@class = "H.3.3"] for attributes //*[] * as a wildcard; for attributes XIRQL IR extensions for XQL document-centric view Slide 9 supports structural and content-based queries Features: Relevance-oriented search Data types and vague search predicates Semantic relativism 7

8 XIRQL: Relevance-oriented search probabilistic indexing of document content Slide 10 weighting of query conditions result of XIRQL queries: ranking of document nodes content-oriented search: retrieve those parts of documents which are most specic w. r. t. query XIRQL: Relevance-oriented search (2) pubyear="1999" book class="h.3.3" Slide 11 author title chapter chapter John Smith This... section section XML Retrieval Introduction XML Query Language XQL We describe syntax of XQL Examples Syntax 4 5 8

9 XIRQL: Data types and vague search predicates markup of data types (e. g. text, person-name, date Slide 12 data type specic (vague) predicates for searching Examples: /book[./description $contains-word$ "IR"] /book[./author $sounds-like$ "fuhr"] /book[./pubyear $around$ "2000"] XIRQL: Semantic relativism <book year="2000"/> vs. <book><year>2000</year></book> Slide 13 > "2000"] vs. /book[year > "2000"] In XIRQL: /book[ pubyear > "2000"] similar for data types, e. g. search for persons without reecting attribute / element names: /book[#person-name $sounds-like$ "fuhr"] 9

10 XIRQL: Outlook Slide 14 Algebra for processing XIRQL queries currently implemented within the Carmen project still missing: appropriate presentation of search results still missing: data-centric view, restructuring search results Quilt [Chamberlin et al. 00], References Slide 15 XML-QL [Deutsch et al. 98] request, ) (W3C submission XPath (W3C recommendation, ) XQL XIRQL [Fuhr & Grojohann 01] 10

11 References Slide 16 Chamberlin, D.; Robie, J.; Florescu, D. (2000). Quilt: An XML query language for heterogeneous data sources. In: WebDB (Informal Proceedings), pages Deutsch, A.; Fernandez, M.; Florescu, D.; Levy, A.; Suciu, D. (1998). XML-QL: A Query Language for XML. In: Marchiori, M. (ed.): QL'98 The Query Languages Workshop. W3C. Fuhr, N.; Grojohann, K. (2001). XIRQL: A Query Language for Information Retrieval in XML Documents. (Submitted for publication). 11