4/15/2002Bo Du 1 - Bo Du, April 15, 2002

XML - QL A Query Language for XML

4/15/2002Bo Du 3 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo 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

4/15/2002Bo Du 5 Useful References ……

4/15/2002Bo 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!!!

4/15/2002Bo Du 7 What does XML-QL do exactly?  Extraction - of data pieces from XML documents  Transformation - Map XML data between different DTDs  Integration/Combination of XML data from different sources

4/15/2002Bo Du 8 How will data be extracted from large XML documents?

4/15/2002Bo Du 9 Data Transformation

4/15/2002Bo Du 10 Data Integration

4/15/2002Bo Du 11 Requirements for the XML Query Language Selection and extraction Preserve structure Reduction Restructuring Join (more detail in next section)

4/15/2002Bo Du 12 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo Du 13 Bib.xml An Introduction to Database Systems Date Addison-Wesley Foundation for Object/Relational Databases: The Third Manifesto Date Darwen Addison-Wesley

4/15/2002Bo Du 14 Bib.dtd

4/15/2002Bo Du 15 Basic Examples: Selection/Extraction Find all the names of the authors whose publisher is Addison-Wesley: WHERE Addison-Wesley $t $a IN " CONSTRUCT $a

4/15/2002Bo Du 16 Basic Examples(contd.) The use of instead of : WHERE Addison-Wesley $t $a IN " CONSTRUCT $a

4/15/2002Bo Du 17 Results of our first query The output is in XML form: Date Darwen Date

4/15/2002Bo Du 18 Use the current XML to construct a new XML structure An Introduction to DB Systems Date Addison-Wesley Foundations for OR Databases Date Darwen Addison-Wesley

4/15/2002Bo Du 19 Construct new XML data (Query) WHERE Addison-Wesley $t $a IN " CONSTRUCT $a $t

4/15/2002Bo Du 20 Construct new XML data (Result) Date An Introduction to DB Systems Date Foundation for OR Databases Darwen Foundation for OR Databases

4/15/2002Bo Du 21 Grouping with Nested Queries: Preserve structure WHERE $p IN " Addison-Wesley IN $p, $t IN $p CONSTRUCT $t WHERE $a IN $p CONSTRUCT $a

4/15/2002Bo Du 22 Reduction of previous slide Where Addition-wesley $t Element_As $x  $a Element_As $y  IN Construct $x $y

4/15/2002Bo Du 23 Another way: WHERE Addison-Wesley $t CONTENT_AS $p IN " CONSTRUCT $t WHERE $a IN $p CONSTRUCT $a

4/15/2002Bo Du 24 Result An Introduction to Database Systems Date Foundation for Object/Relational Databases: The Third Manifesto Date Darwen

4/15/2002Bo Du 25 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo 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)

4/15/2002Bo Du 27 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo 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

4/15/2002Bo Du 29 Tag variables WHERE -- $p can be {article, book} $t 1995 Date IN "bib.xml", $e IN {author, editor} CONSTRUCT $t Date All publications published in 1995 in which Date is either an author, or an editor

4/15/2002Bo Du 30 Query result Date An Introduction to Database Systems Date The New Jersey Machine-Code Toolkit

4/15/2002Bo Du 31 payroll.xml J. Doe M. Smith R. Johnson P. Kent 33000

4/15/2002Bo Du 32 taxpayers.xml

4/15/2002Bo Du 33 Integrating data from multiple XML sources WHERE ELEMENT_AS $n $ssn IN ”payroll.xml", -- take a look at payroll.XML $ssn ELEMENT_AS $i IN "taxpayers.xml” -- take a look at taxpayer.xml CONSTRUCT $n $i

4/15/2002Bo Du 34 Integration result J. Doe M.Smith R. Johnson

4/15/2002Bo Du 35 Functions definitions and DTDs function query() { CONSTRUCT findDeclaredIncomes("taxpayers.xml","payroll.xml") } function findDeclaredIncome($Taxpayers,$Employees) { WHERE $s $x IN $Taxpayer, $s $n IN $Employees CONSTRUCT $n $x }

4/15/2002Bo Du 36 Functions definitions and DTDs (cont) Restrictions by DTD’s: function findDeclaredIncome ( $Taxpayers:” $Employees:” dtd” :“ ) { WHERE …. CONSTRUCT …. }

4/15/2002Bo Du 37 Embedding queries in data WHERE $t $y IN “ $y > 1995 CONSTRUCT $t WHERE $t $y IN “ $y >1995 CONSTRUCT $t

4/15/2002Bo Du 38 Indexes for element: XML support element-order variables. Example: … here $i and $j are bind to an integer 0, 1, 2 … that represent the index in the local order of the edges.

4/15/2002Bo Du 39 Indexes for element (graph) (year=“1995”) book [0] book[1] title[0] author[2] publisher[1] title[0] author[3] author[2] name[0] An introduction … Addison- Wesley Foundations for... name[0] lastname[0] Date Datwen lastname[0] publisher[1] (year=“1998”) ( 1 ) ( 13 ) ( 12 ) ( 11 ) ( 10 ) ( 9 ) ( 8 ) ( 7 ) ( 5 ) ( 6 ) ( 4)( 3 ) ( 2 ) ( 15 ) ( 14 ) root

4/15/2002Bo Du 40 Indexes for element: (cont.) Example : retrieves all the persons whose lastname precedes the firstname : WHERE $p IN “ $x IN $p, $y IN $p, $j < $k CONSTRUCT $p

4/15/2002Bo Du 41 ORDER-BY: (cont.) Reverse the order of all authors in a publication: WHERE $p IN “ CONSTRUCT WHERE $a IN $p ORDER-BY $k DESCENDING CONSTRUCT $a WHERE $v IN $p $e != “author” CONSTRUCT $v

4/15/2002Bo Du 42 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo Du 43 Extensions and open issues: Entities User-defined predicates String regular expressions Name spaces Aggregates XML syntax Extensions to other XML-related standard

4/15/2002Bo Du 44 OUTLINE  Introduction * Examples in XML-QL * A Data Model for XML * Advanced Examples in XML-QL * Extensions and Open Issues  Summary

4/15/2002Bo 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

4/15/2002Bo Du 46 End ???…