cotton

Querying XML Documents: 

Querying XML Documents Paul Cotton, Microsoft Canada XML 2003, Philadelphia Dec 11, 2003

Organization of Presentation: 

Organization of Presentation XML query history XML Query WG history, goals and status XML Query working drafts XQuery overview XQuery status and outstanding issues Questions

XML query history : 

XML query history Early queries facilities for SGML 1998: “roll your own query language” Feb 1998: XQL proposal http://metalab.unc.edu/xql Aug 1998: XML-QL submission http://www.w3.org/TR/NOTE-xml-ql/ Dec 1998: W3C QL’98 Workshop http://www.w3.org/TandS/QL/QL98 Nov 1999: XPath Recommendation http://www.w3.org/TR/xpath

W3C XML Query WG - History : 

W3C XML Query WG - History July 1999: Working Group proposed as part of XML Activity Phase 3 rechartering Sept 1999: WG chartered and first F2F July 2002: Re-chartered with XML Activity Currently 26 W3C member companies 25 F2F meetings and 160+ telcons so far Public WDs every three months Last Call Working Drafts published Nov 2003 Seven documents on Recommendation track

W3C XML Query WG - Goals: 

W3C XML Query WG - Goals “The goal of the XML Query WG is to produce a data model for XML documents, a set of query operators on that data model, and a query language based on these query operators.”

XML Query Requirements WD: 

XML Query Requirements WD General Requirements Non-procedural query language XML syntax for query language but also a readable syntax Protocol independent Standard error conditions Future support for updates XML Query Data Model Requirements Built on XML Infoset and PSVI Namespace aware Support for XML Schema data types Support for inter- and intra- document references (NOT in V1)

XML Query Requirements WD : 

XML Query Requirements WD XML Query Functionality Operators on all data types Text operators across element boundaries Support for hierarchy and sequence Ability to combine data from different locs Aggregation and sorting Combination of operators including queries as operands Support for NULL/empty values Structural preservations Identity preservation Operations on names Operations on “schemas” (NOT in V1) Extensibility Closure Revised to match Last Call WDs in Nov 2003

XML Query Use Cases WD: 

XML Query Use Cases WD Use Case Organization Description, DTD/Schema, Input Data, Queries and Results Current Use Cases "XMP": Experiences and Exemplars "TREE": Queries that preserve hierarchy "SEQ" - Queries based on Sequence "R" - Access to Relational Data “SGML" – Queries from SGML Open 1992 “STRING": String Search "NS" - Queries Using Namespaces "PARTS" - Recursive Parts Explosion “STRONG” – Queries that exploit strongly typed data Necessary but not sufficient set of tests for XQuery implementations Revised with each set of Working Drafts

XML Query 1.0 Data Model WD: 

XML Query 1.0 Data Model WD Defines what information is available to an XML Query 1.0, XSLT 2.0 or XPath 2.0 processor Published jointly with XSL Working Group Infoset plus the following: Support for XML Schema data types (PSVI) Support for document collections Node-labelled tree constructor model with node identity Mapping from Infoset to Query Data Model uses Infoset terminology and is shown by example 1st Last Call May 2003, now in 2nd Last Call

XML Query 1.0 Formal Semantics WD: 

XML Query 1.0 Formal Semantics WD XML Query Formal Semantics is used: to define XQuery and XPath static typing to define XQuery and XPath runtime semantics FS defines both static and dynamic semantics static semantics are presented as type inference rules, which relate XQuery/FS expressions to types dynamic, or operational, semantics are presented as value inference rules, which relate XQuery/FS expressions to values in the XML Query Data Model Last Call Working Draft expected in Jan 2004

XQuery: A Query Language for XML: 

XQuery: A Query Language for XML XQuery is a functional language in which a query is represented as an expression XQuery expressions can be nested with full generality The input and output of an XQuery are instances of the XML Query Data Model Based on OQL, SQL, XML-QL, XPath Readable syntax Proper superset of XPath 2.0 Last Call Working Draft, Nov 2003

XQueryX: 

XQueryX XQueryX is an XML representation of an XQuery It was created by mapping the productions of the XQuery BNF directly into XML productions XQueryX useful to enable: Parser reuse Queries on queries Generation of queries Embedding of queries in XML documents XQueryX status – Issue 152 Revised Working Draft expected in Dec 2003

XQuery Function and Operators WD: 

XQuery Function and Operators WD XML Query Functions and Operators is used: to defines basic operators and functions on the datatypes defined in XML Schema Part 2: Datatypes for use in XQuery, XPath, XSLT and other related XML standards to define operators and functions on nodes and node sequences as defined in the XQuery 1.0 and XPath 2.0 Data Model for use in XQuery, XPath, XSLT and other related XML standards Includes several new data types derived from XML Schema data types 1st Last Call May 2003, now in 2nd Last Call

XSLT and XQuery Serialization WD: 

XSLT and XQuery Serialization WD XSLT and XQuery Serialization WD Based on material from XSLT 1.0 Now common to XSLT 2.0 and XQuery 1.0 Defines how to convert a Data Model instance into a set of octets in XML, HTML, XHTML or text Last Call Working Draft, Nov 2003

XQuery Expressions: 

XQuery Expressions XQuery expressions Path expressions Element constructors FLWOR expressions Expressions involving operators and functions Conditional expressions Quantified expressions List constructors Expressions that test or modify datatypes

XQuery Path Expressions: 

XQuery Path Expressions Based on abbreviated syntax of XPath Select the second section of the fifth chapter of the doc /doc/chapter[5]/section[2]

XQuery Element Constructors: 

XQuery Element Constructors XQuery element constructor consists of a start tag and an end tag, enclosing an optional list of expressions that provide the content of the element. Generate an <emp>element that has an “empid” attribute. The value of the attribute and the content of the element are specified by variables that are bound in other parts of the query. <emp empid = {$id}> {$name} {$job} </emp>

XQuery FLWOR Expressions: 

XQuery FLWOR Expressions A FLWOR expression binds some expressions, applies an optional predicate and ordering, and constructs a new result. FOR and LET clauses generate a list of tuples of bound expressions, preserving document order. WHERE clause applies a predicate, eliminating some of the tuples RETURN clause is executed for each surviving tuple, generating an ordered list of outputs

XQuery FLWOR Expressions: 

XQuery FLWOR Expressions List the titles of books published by Morgan Kaufmann in 1998. FOR $b IN doc("bib.xml")//book WHERE $b/publisher = "Morgan Kaufmann" AND $b/year = "1998" RETURN $b/title List each publisher and the average price of its books. FOR $p IN distinct(doc("bib.xml")//publisher) LET $a := avg(doc("bib.xml") /book[publisher = $p]/price) RETURN <publisher> <name> {$p/text()} </name> <avgprice> {$a} </avgprice> </publisher>

XQuery Operators and Functions: 

XQuery Operators and Functions Infix and prefix operators Parenthesized expressions Arithmetic and logical operators Sequence operators UNION, INTERSECT and EXCEPT Functions can be defined in XQuery WDs support definition and import of modules of functions

XQuery Operators and Functions: 

XQuery Operators and Functions Find the maximum depth of the document named "partlist.xml." NAMESPACE xsd="http://www.w3.org/2001/XMLSchema-datatypes" DEFINE FUNCTION depth($e AS ELEMENT) AS xsd:integer { {-- An empty element has depth 1 --} {-- Otherwise, add 1 to max depth of children --} IF empty($e/*) THEN 1 ELSE max(FOR $c in $e/* RETURN depth($c)) + 1 } depth(doc("partlist.xml"))

XQuery Conditional Expressions: 

XQuery Conditional Expressions IF THEN ELSE construct Make a list of holdings. For journals, include the editor, and for all other holdings, include the author. FOR $h IN //holding RETURN <holding> {$h/title, IF $h/@type = "Journal" THEN $h/editor ELSE $h/author } </holding>

XQuery Quantified Expressions: 

XQuery Quantified Expressions Existential and Universal quantifiers Find titles of books in which both sailing and windsurfing are mentioned in the same paragraph. FOR $b IN //book WHERE SOME $p IN $b//para SATISFIES contains($p, "sailing") AND contains($p, "windsurfing") RETURN $b/title Find titles of books in which sailing is mentioned in every paragraph. FOR $b IN //book WHERE EVERY $p IN $b//para SATISFIES contains($p, "sailing") RETURN $b/title

Sequence-related Operators: 

Sequence-related Operators A sequence may be constructed by enclosing zero or more expressions separated by commas. For example: ($x, $y, $z) denotes a sequence containing three members represented by variables >> (precedes) and << (follows) boolean functions () denotes an empty sequence.

XQuery Operators on Data Types: 

XQuery Operators on Data Types INSTANCE OF returns True if its first operand is an instance of the type named in its second operand CAST is used to convert a value from one data type to another TREAT AS causes the query processor to treat an expression as though its data type were a subtype of its static type VALIDATE executes XML Schema validation

W3C XML Query WG - Status : 

W3C XML Query WG - Status Requirements and Use Cases (Nov 2003) XML Query (XQuery) Requirements http://www.w3.org/TR/xquery-requirements XML Query Use Cases http://www.w3.org/TR/xmlquery-use-cases/ XQuery and XPath Full-Text Requirements http://www.w3.org/TR/xquery-full-text-requirements/ XQueryX (June 2001 and later in Dec 2003) XML Syntax for XQuery 1.0: XQueryX http://www.w3.org/TR/xqueryx

W3C XML Query WG - Status : 

W3C XML Query WG - Status Last Call Working Drafts (Nov 2003) XQuery 1.0: An XML Query Language http://www.w3.org/TR/xquery/ XML Path Language (XPath) 2.0 http://www.w3.org/TR/xpath20/ XML Query 1.0 and XPath 2.0 Formal Semantics http://www.w3.org/TR/xquery-semantics/ XML Query 1.0 and XPath 2.0 Functions and Operators http://www.w3.org/TR/xpath-functions/ XML Query 1.0 and XPath 2.0 Data Model http://www.w3.org/TR/xpath-datamodel/ XSLT 2.0 and XQuery 1.0 Serialization http://www.w3.org/TR/xslt-xquery-serialization/ Next publication status WG Charter status http://www.w3.org/2001/12/xmlbp/xml-query-wg-charter.html

Current XQuery Issues: 

Current XQuery Issues XQueryX Issue 152. What is best XML syntax for XQuery? Need to close 2 issues to get Formal Semantics to Last Call Issue 555 Formal Semantics of Module Import Issue 559 New Sequence Type needs to be fully implemented in FS

Future XQuery Work: 

Future XQuery Work Support for full-text retrieval XQuery test suite (needed for CR) Support for an update language

Full-Text Support in XQuery: 

Full-Text Support in XQuery Full-Text issues history within XML Query WG Library of Congress Use Case http://lcweb.loc.gov/crsinfo/xml/lc_usecases.html related to I18N issues Is cross-language definition of characters, words, sentences or paragraphs feasible? XQuery and XPath Full-Text Requirements http://www.w3.org/TR/xquery-full-text-requirements XQuery and XPath Full-Text Use Cases http://www.w3.org/TR/xmlquery-full-text-use-cases/ Target is XML Query 1.1

Early XQuery implementations (1): 

Early XQuery implementations (1) BEA's Liquid Data: http://edocs.bea.com/liquiddata/docs10/prodover/concepts.html Bluestream Database Software Corp.'s XStreamDB: http://www.bluestream.com/dr/?page=Home/Products/XStreamDB/ Cerisent's XQE: http://cerisent.com/cerisent-xqe.html Cognetic Systems's XQuantum: http://www.cogneticsystems.com/xquery/xquery.html Fatdog's XQEngine: http://www.fatdog.com/ GAEL's Derby: http://www.gael.fr/derby/ GNU's Qexo (Kawa-Query): http://www.qexo.org/ Ipedo's XML Database v3.0: http://www.ipedo.com IPSI's IPSI-XQ: http://ipsi.fhg.de/oasys/projects/ipsi-xq/index_e.html Lucent's Galax: http://db.bell-labs.com/galax/ Microsoft's XML Query Language Demo: http://xqueryservices.com Nimble Technology's Nimble Integration Suite: http://www.nimble.com/ OpenLink Software's Virtuoso Universal Server: http://demo.openlinksw.com:8890/xqdemo Oracle's XML DB: http://otn.oracle.com/tech/xml/xmldb/htdocs/querying_xml … (continued on next slide)

Early XQuery implementations (2): 

Early XQuery implementations (2) Politecnico di Milano's XQBE: http://dbgroup.elet.polimi.it/xquery/xqbedownload.html QuiLogic's SQL/XML-IMDB: http://www.quilogic.cc/xml.htm Software AG's Tamino XML Server: http://www.softwareag.com/tamino/News/tamino_41.htm Tamino XML Query Demo: http://tamino.demozone.softwareag.com/demoXQuery/index.html Sonic Software's Stylus Studio 5.0 (XQuery, XML Schema and XSLT IDE): http://www.stylusstudio.com Sonic XML Server: http://www.sonicsoftware.com/products/additional_software/extensible_information_server/ Sourceforge's Saxon: http://saxon.sourceforge.net/ SourceForge's XQuench: http://xquench.sourceforge.net/ SourceForge's XQuery Lite: http://sourceforge.net/projects/phpxmlclasses/ Worcester Polytechnic Institute's RainbowCore: http://davis.wpi.edu/~dsrg/rainbow/ Xavier C. Franc's Qizx/Open: http://www.xfra.net/qizxopen X-Hive's XQuery demo: http://www.x-hive.com/xquery XML Global's GoXML DB: http://www.xmlglobal.com/prod/xmlworkbench/ XQuark Group and Université de Versailles Saint-Quentin's: http://forge.objectweb.org/project/showfiles.php?group_id=78 … (see http://www.w3.org/XML/Query#products)

XQuery/XPath Grammars: 

XQuery/XPath Grammars W3C's Grammar Test Pages XQuery 1.0 Grammar Test Page http://www.w3.org/2003/11/applets/xqueryApplet.html XPath 2.0 Grammar Test Page http://www.w3.org/2003/11/applets/xpathApplet.html

Questions: 

Questions Today Later: pcotton@microsoft.com Feedback email and Last Call comments list: public-qt-comments@w3.org (archived at http://lists.w3.org/Archives/Public/public-qt-comments/). Public discussion email list: www-ql@w3.org