4/15/2002Bo Du 1 - Bo Du, April 15, 2002. XML - QL A Query Language for XML

4/15/2002 Bo Du 1

- Bo Du, April 15, 2002

XML - QL

A Query Language for XML

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OUTLINE Introduction

Examples in XML-QL

A Data Model for XML

Advanced Examples in XML-QL

Extensions and Open Issues

Summary

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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

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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/ ……

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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!!!

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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

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How will data be extracted from large XML documents?

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Data Transformation

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Data Integration

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Requirements for the XML Query Language Selection and extraction Preserve structure Reduction Restructuring Join

(more detail in next section)

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Examples in XML-QL




Summary

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Bib.xml<bib> <book year="1995">

<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 ThirdManifesto </title>

<author> <lastname> Date </lastname> </author><author> <lastname> Darwen </lastname> </author><publisher> <name> Addison-Wesley </name > </publisher>

</book></bib>

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Bib.dtd

<!ELEMENT book (author+, title, publisher)>

<!ATTLIST book year CDATA>

<!ELEMENT article (author+, title, year?, (shortversion|longversion))>

<!ATTLIST article type CDATA>

<!ELEMENT publisher (name, address)>

<!ELEMENT author (firstname?, lastname)>

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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

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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

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Results of our first queryThe output is in XML form:

<lastname> Date </lastname>

<lastname> Darwen </lastname>

<lastname> Date </lastname>

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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>

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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 </>

</>

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Construct new XML data (Result)<result>

<author> <lastname> Date </lastname> </author>

<title> An Introduction to DB Systems </title>

</result>

<result>


<title> Foundation for OR Databases</title>

</result>

<result>

<author> <lastname> Darwen </lastname> </author>

<title> Foundation for OR Databases</title>

</result>

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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 </>

</>

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Reduction of previous slideWhere

<book> <publisher> <name>Addition-wesley</> </>

<title>$t </> Element_As $x <author> $a</> Element_As $y </> </> IN www.a.b.c/bib/xml

Construct <result> $x $y </>

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Another way:WHERE <book>

<publisher> <name>Addison-Wesley</> </>

<title> $t </>

</> CONTENT_AS $p IN "www.a.b.c/bib.xml”

CONSTRUCT <result>

<title> $t </>

WHERE <author> $a </> IN $p

CONSTRUCT <author> $a </>

</>

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Result<result>

<title> An Introduction to Database Systems </title>


</result>

<result>

<title> Foundation for Object/Relational Databases: The Third Manifesto </title>


<author> <lastname> Darwen </lastname> </author>

</result>

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Examples in XML-QL




Summary

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XML Data model

XML Graph Syntax for Data Mapping of XML graphs into XML

documents Element identities an ID references ……

(talked in previous presentations)

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Examples in XML-QL




Summary

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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

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Tag variablesWHERE < $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

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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>

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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>

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taxpayers.xml<IRS>

<taxpayer> <ssn>100-00-0001</ssn><income>35000</income><taxes>7000</taxes> </taxpayer>


<taxpayer><ssn>100-00-0003</ssn><income>1430000</income><taxes>25000</taxes> </taxpayer>


</IRS>

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Integrating data from multiple XML sourcesWHERE <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.xmlCONSTRUCT <result> $n $i </>

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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>

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Functions definitions and DTDsfunction 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 </> </>}

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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 ….

}

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Embedding queries in data<result>

<articles>WHERE <article> <title> $t </><year> $y </>

</> IN “www.a.b.c/bib.xml”, $y > 1995CONSTRUCT <title> $t </>

</><books>

WHERE <book> <title> $t </> <year> $y </> </> IN “www.a.b.c/bib.xml”, $y >1995

CONSTRUCT <title> $t </> </>

</>

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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.

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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

Addison-Wesley

Foundations for ...

name[0] lastname[0]

DateDate Datwen

lastname[0]

lastname[0]

publisher[1]

(year=“1998”)

( 1 )

( 13 )

( 12 )

( 11 )

( 10 )( 9 )

( 8 )

( 7 )( 5 )

( 6 )( 4)( 3 )

( 2 )

( 15 )

( 14 )

root

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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 </>

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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 $pORDER-BY $k DESCENDINGCONSTRUCT <author> $a </>WHERE < $e > $v </> IN $p

$e != “author”CONSTRUCT <$e> $v </>

</pub>

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Examples in XML-QL




Summary

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Extensions and open issues:

Entities User-defined predicates String regular expressions Name spaces Aggregates XML syntax Extensions to other XML-related standard

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Examples in XML-QL




Summary

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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

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End

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Documents

4/15/2002Bo Du 1 - Bo Du, April 15, 2002. XML - QL A Query Language for XML