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XML-QL: Query Language for XML

XML-QL is a query language for extracting, transforming, and integrating data from large XML documents, with examples and a data model for XML.

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XML-QL: Query Language for XML

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  1. - Bo Du, April 15, 2002 Bo Du

  2. XML - QL A Query Language for XML

  3. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  4. Why do we need a query language • XML standard doesn't address: • Extraction : How will data be extracted from large XML documents? • Transformation : How will XML data be exchanged between user communities using different but related DTDs? • Integration : How will XML data from multiple XML sources be integrated? • Conversion of data between relational or OO to XML Bo Du

  5. Useful References • http://www.w3.org/XML/Query • http://www.w3.org/TR/NOTE-xml-ql/ • http://www.ibiblio.org/xql/ • http://groups.yahoo.com/group/xml-dev/ • …… Bo Du

  6. Is this X?L a standard? NO! It is a submission to the World Wide Web Consortium. It is intended for review and comment by W3C members and is subject to change!!! Bo Du

  7. What does XML-QL do exactly? • Extraction - of data pieces from XML documents • Transformation - Map XML data between different DTDs • Integration/Combinationof XML data from different sources Bo Du

  8. How will data be extracted from large XML documents? Bo Du

  9. DataTransformation Bo Du

  10. Data Integration Bo Du

  11. Requirements for the XML Query Language • Selection and extraction • Preserve structure • Reduction • Restructuring • Join (more detail in next section) Bo Du

  12. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  13. Bib.xml <bib> <book year="1995"> <!-- A good introductory text --> <title> An Introduction to Database Systems </title> <author> <lastname> Date </lastname> </author> <publisher><name> Addison-Wesley </name ></publisher> </book> <book year="1998"> <title> Foundation for Object/Relational Databases: The Third Manifesto </title> <author> <lastname> Date </lastname> </author> <author> <lastname> Darwen </lastname> </author> <publisher> <name> Addison-Wesley </name > </publisher> </book> </bib> Bo Du

  14. Bib.dtd <!ELEMENTbook (author+, title, publisher)> <!ATTLIST book year CDATA> <!ELEMENTarticle (author+, title, year?, (shortversion|longversion))> <!ATTLISTarticle type CDATA> <!ELEMENTpublisher (name, address)> <!ELEMENT author (firstname?, lastname)> Bo Du

  15. Basic Examples: Selection/Extraction Find all the names of the authors whose publisher is Addison-Wesley: WHERE <book> <publisher><name> Addison-Wesley </name></publisher> <title> $t</title> <author> $a</author> </book> IN"www.a.b.c/bib.xml" CONSTRUCT$a Bo Du

  16. Basic Examples(contd.) The use of </> instead of </XXX>: WHERE <book> <publisher><name> Addison-Wesley</></> <title> $t</> <author> $a</> </>IN"www.a.b.c/bib.xml" CONSTRUCT$a Bo Du

  17. Results of our first query The output is in XML form: <lastname> Date </lastname> <lastname>Darwen </lastname> <lastname> Date </lastname> Bo Du

  18. Use the current XML to construct a new XML structure <bib> <book year=“1995> <title> An Introduction to DB Systems </title> <author> <lastname> Date </lastname></author> <publisher><name> Addison-Wesley</name> </publisher> </book> <book year=“1995> <title> Foundations for OR Databases </title> <author> <lastname> Date </lastname></author> <author> <lastname> Darwen </lastname></author> <publisher><name> Addison-Wesley</name> </publisher> </book> </bib> Bo Du

  19. Construct new XML data (Query) WHERE <book> <publisher> <name> Addison-Wesley</></> <title> $t </> <author> $a </> </> IN"www.a.b.c/bib.xml" CONSTRUCT<result> <author> $a </> <title> $t </> </> Bo Du

  20. Construct new XML data (Result) <result> <author> <lastname> Date</lastname> </author> <title>An Introduction to DB Systems</title> </result> <result> <author> <lastname>Date</lastname> </author> <title>Foundation for OR Databases</title> </result> <result> <author> <lastname>Darwen</lastname> </author> <title>Foundation for OR Databases</title> </result> Bo Du

  21. Grouping with Nested Queries: Preserve structure WHERE <book> $p </book>IN"www.a.b.c/bib.xml”, <publisher> <name>Addison-Wesley</> </> IN$p, <title> $t </> IN $p CONSTRUCT <result> <title> $t </> WHERE <author> $a </> IN$p CONSTRUCT <author> $a </> </> Bo Du

  22. Reduction of previous slide Where <book> <publisher> <name>Addition-wesley</> </> <title>$t </> Element_As $x  <author> $a</> Element_As $y  </> </> INwww.a.b.c/bib/xml Construct <result> $x $y </> Bo Du

  23. Another way: WHERE <book> <publisher> <name>Addison-Wesley</> </> <title> $t </> </> CONTENT_AS$pIN"www.a.b.c/bib.xml” CONSTRUCT <result> <title> $t </> WHERE <author> $a </> IN$p CONSTRUCT <author> $a </> </> Bo Du

  24. Result <result> <title> An Introduction to Database Systems </title> <author> <lastname> Date </lastname> </author> </result> <result> <title> Foundation for Object/Relational Databases: The Third Manifesto </title> <author> <lastname> Date </lastname> </author> <author> <lastname>Darwen </lastname> </author> </result> Bo Du

  25. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  26. XML Data model • XML Graph • Syntax for Data • Mapping of XML graphs into XML documents • Element identities an ID references • …… (talked in previous presentations) Bo Du

  27. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  28. Advanced examples in XML-QL • Tag Variables • Regular - path Expressions • Transforming XML data • Integrating from multiple XML sources • Functions definitions and DTDs • External functions • Ordered model - Sorting, Indexing Bo Du

  29. Tag variables WHERE< $p > -- $p can be {article, book} <title> $t </> <year>1995 </> < $e ><lastname> Date </> </> </> IN "bib.xml", $e IN {author, editor} CONSTRUCT < $p > <title> $t </> < $e > Date </> </> All publications published in 1995 in which Date is either an author, or an editor Bo Du

  30. Query result <book> <author>Date</author> <title>An Introduction to Database Systems</title> </book> <article> <author>Date</author> <title>The New Jersey Machine-Code Toolkit</title> </article> Bo Du

  31. payroll.xml <Payroll> <person> <ssn>100-00-0001</ssn> <name>J. Doe</name> <salary>35000</salary> </person> <person> <ssn>100-00-0002</ssn> <name>M. Smith</name> <salary>73000</salary> </person> <person> <ssn>100-00-0003</ssn> <name>R. Johnson</name> <salary>1400000</salary> </person> <person> <ssn>100-00-0004</ssn> <name>P. Kent</name> <salary>33000</salary> </person> </Payroll> Bo Du

  32. taxpayers.xml <IRS> <taxpayer> <ssn>100-00-0001</ssn> <income>35000</income> <taxes>7000</taxes> </taxpayer> <taxpayer> <ssn>100-00-0002</ssn> <income>55000</income> <taxes>3000</taxes> </taxpayer> <taxpayer> <ssn>100-00-0003</ssn> <income>1430000</income> <taxes>25000</taxes> </taxpayer> <taxpayer> <ssn>100-00-0005</ssn> <income>120000</income> <taxes>30000</taxes> </taxpayer> </IRS> Bo Du

  33. Integrating data from multiple XML sources WHERE <person> <name></> ELEMENT_AS$n <ssn> $ssn</> </> IN”payroll.xml",-- take a look at payroll.XML <taxpayer> <ssn> $ssn </> <income></> ELEMENT_AS$i </> IN"taxpayers.xml”-- take a look at taxpayer.xml CONSTRUCT <result> $n $i </> Bo Du

  34. Integration result <result> <income>35000</income> <name>J. Doe</name> </result> <result> <income>55000</income> <name>M.Smith</name> </result> <result> <income>1430000</income> <name>R. Johnson</name> </result> Bo Du

  35. Functions definitions and DTDs function query() { CONSTRUCT <result> findDeclaredIncomes("taxpayers.xml","payroll.xml") </result> } function findDeclaredIncome($Taxpayers,$Employees) { WHERE <taxpayer><ssn>$s</> <income> $x </></> IN $Taxpayer, <employee><ssn> $s </> <name> $n </> </>IN$Employees CONSTRUCT<result><name> $n </><income> $x </> </> } Bo Du

  36. Functions definitions and DTDs (cont) Restrictions by DTD’s: function findDeclaredIncome ( $Taxpayers:”www.irs.gov/tp.dtd”, $Employees:”www.employees.org/employeess.dtd” :“www.my.site.com/myresult.dtd” ) { WHERE …. CONSTRUCT …. } Bo Du

  37. Embedding queries in data <result> <articles> WHERE <article> <title> $t </><year> $y </> </> IN “www.a.b.c/bib.xml”, $y > 1995 CONSTRUCT <title> $t </> </> <books> WHERE <book> <title> $t </> <year> $y </> </> IN “www.a.b.c/bib.xml”, $y>1995 CONSTRUCT <title> $t </> </> </> Bo Du

  38. Indexes for element: • XML support element-order variables. • Example: <a[$i]> … </> <$x[$j]> … </> • here $i and $j are bind to an integer 0, 1, 2 … that represent the index in the local order of the edges. Bo Du

  39. Indexes for element (graph) root book [0] book[1] ( 1 ) ( 8 ) (year=“1998”) ( 2 ) (year=“1995”) author[3] title[0] author[2] ( 14 ) title[0] publisher[1] author[2] publisher[1] ( 9 ) ( 10 ) ( 12 ) ( 6 ) ( 3 ) ( 4) Foundations for ... lastname[0] An introduction … lastname[0] name[0] lastname[0] ( 13 ) name[0] ( 11 ) ( 15 ) ( 5 ) Date Datwen ( 7 ) Addison-Wesley Addison-Wesley Date Bo Du

  40. Indexes for element: (cont.) Example: retrieves all the persons whose lastname precedes the firstname: WHERE <person> $p </> IN“www.a.b.c/people.xml” <firstname [$k] > $x </>IN$p, <lastname[$j] > $y </>IN$p, $j < $k CONSTRUCT <person> $p </> Bo Du

  41. ORDER-BY: (cont.) Reverse the order of all authors in a publication: WHERE <pub> $p </>IN“www.a.b.c/people.xml”, CONSTRUCT <pub> WHERE<author[$k]> $a </> IN$p ORDER-BY $k DESCENDING CONSTRUCT <author> $a </> WHERE < $e > $v </> IN$p $e != “author” CONSTRUCT <$e> $v </> </pub> Bo Du

  42. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  43. Extensions and open issues: • Entities • User-defined predicates • String regular expressions • Name spaces • Aggregates • XML syntax • Extensions to other XML-related standard Bo Du

  44. OUTLINE • Introduction • Examples in XML-QL • A Data Model for XML • Advanced Examples in XML-QL • Extensions and Open Issues • Summary Bo Du

  45. Summary/Conclusions • XML-QL is a declarative language which provides support for querying, constructing, transforming, and integrating XML data • XML-QL supports both ordered and unordered view on XML document • XML-QL is based on similar database research suggested model of Semi-structured data • XML-QL satisfy the absolute set of requirements from query language cited in XML Query Requirements of W3C Working Draft • XML-QL is good candidate to be the new XML standard query language Bo Du

  46. End ???… Bo Du

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