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Query Languages for XML: XQuery

Query Languages for XML: XQuery. Adrian Pop, Paul Pop Computer and Information Science Dept. Linköpings universitet. Outline. Motivation XML applications, types of queries Approaches Requirements on a query language Path expressions, the basic building block

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Query Languages for XML: XQuery

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  1. Query Languages for XML: XQuery Adrian Pop, Paul PopComputer and Information Science Dept.Linköpings universitet

  2. Outline • Motivation • XML applications, types of queries • Approaches • Requirements on a query language • Path expressions, the basic building block • XML query languages: XML-QL, YATL, Lorel, XQL • XQuery • Background, history • Concepts, examples • FLWR expressions • FOR and LET expressions • Collections and sorting • Available software, demo • Examples • XQuery vs. XSLT • Summary

  3. Motivation • XML applications • Representing many types of information, many sources • Structured and semi-structured documents • Relational databases • Object repositories • Information has to be • Accessed, filtered, grouped, transformed, etc. • Query languages are needed! • Retrieve and interpret information • Diverse sources • Querying a database is different from transforming a document

  4. Document World vs. Database World • Two worlds, two querying approaches • XML-as-document • Roots in SGML • Queried using path expressions • XML-as-data • Middleware, interface to databases • Queried with SQL-like constructs • XML query language has to work in both worlds • A query language for XML should work across all types of XML data sources and applications • Problem • Exiting query languages designed for specific types of data • Robust for those types, weak for other

  5. Types of Queries • W3C specification: Important classes of queries • Filtering • Compute a table of contents for a document • Joins • Combine data from multiple sources in a single result • Grouping • Forming data into groups, applying aggregate function like “average” or “count” • Queries on sequence • Queries where the sequence, hierarchy, (i.e. precedence relationships) are important

  6. Requirements on a Query Language • Output: a query language should output XML • Composition of queries! • Views can be defined via a single query • Transparent to applications • Server-side processing • Selection: choosing a document, element, based on content, structure or attributes; • Extraction: pulling out particular elements of a document; • Reduction: removing selected sub-elements of an element; • Restructuring: Constructing a new set of element instances to hold queried data; • Combination: Merging two or more elements into one; • should all be possible in a single query. • No schema required / exploit available schema • Queries should work on XML data when there is no schema, DTD • Use the exiting schema for detecting errors at compile time

  7. Requirements on a Query Language, Cont. • Preserve order and association • A query should preserve the order of elements, grouping • Programmatic manipulation • Queries will be constructed via programs, interfaces; programs should in an easy fashion with the representation of queries • XML representation • Mutually embedding with XML • XLink and XPointer cognizant • Namespace alias independence • A query should not be dependent on namespace aliases local to an XML document • Support for new datatypes • Suitable for metadata

  8. Path Expressions • Query language for XML, semi-structured data • Semi-structured data modeled as a edge-labeled directed graph • Ability to reach to arbitrary depths in the data graph • Achieved using “path expressions” • Path expressions: basic building block of a query language • A sequence of edge labels l1, l2, …, ln • A query, whose result for a given data graph is a set of nodes • Can be specified based on some properties • Property of the path: the path must traverse the book edge • Property of an individual edge label: the label contains the substring “Victor” • Regular expressions are used to describe path properties • Limitations • Cannot create new nodes in the database • Cannot perform “Joins” • Cannot test values stored in a database

  9. Path Expressions Bib &o1 paper paper book references &o12 &o24 &o29 references references author page author year author title http title title publisher author author author &o43 &25 &o44 &o45 &o46 &o52 &96 1997 &o51 &o50 &o49 &o47 &o48 last firstname firstname lastname first lastname &o70 &o71 &243 &206 “Serge” “Abiteboul” “Victor” 122 133 “Vianu” • Data, modeled as an edge-labeleddirected graph Bib.paper={&o12,&o29} Bib.book.publisher={&o51} Bib.paper.author.lastname={&o71,&206}

  10. Regular Path Expressions • R ::= label | _ | R.R | (R|R) | R* | R+ | R? • Examples: • Bib.(paper|book).author • Bib.book.author.lastname? • Bib.book.(references)*.author • Bib.(_)*.zip

  11. XML Query Languages • Semistructured databases • XML-QLA. Deutsch, M. Fernandez, D. Florescu, A. Levy, and D. Suciu. A query language for XML, http://www.research.att.com/~mff/files/final.html • YATLS. Cluet, S. Jacqmin and J. Siméon The New YATL: Design and Specifications. Working draft. • LorelS. Abiteboul, D. Quass, J. McHugh, J. Widom, and J. Wiener. The Lorel query language for semistructured data, ftp://db.stanford.edu/pub/papers/lorel96.ps • Structured text, search techniques • XQLJ. Robie. The design of XQL, 1999, http://www.texcel.no/whitepapers/xql-design.html

  12. XML Query Examples <bib> <book year="1994"> <title>TCP/IP Illustrated</title> <author><last>Stevens</last> <first>W.</first></author> <publisher>Addison-Wesley</publisher> <price>65.95</price> </book> <book year="1992"> <title>Advanced Programming the Unix environment</title> <author><last>Stevens</last><first>W.</first> </author> <publisher>Addison-Wesley</publisher> <price>65.95</price> </book> <book year="2000"> <title>Data on the Web</title> <author><last>Abiteboul</last><first>Serge</first></author> <author><last>Buneman</last><first>Peter</first></author> <author><last>Suciu</last><first>Dan</first></author> <publisher>Morgan Kaufmann Publishers</publisher> <price>39.95</price> </book>- <book year="1999"> <title>The Economics of Technology and Content for Digital TV</title> <editor><last>Gerbarg</last><first>Darcy</first> <affiliation>CITI</affiliation> </editor> <publisher>Kluwer Academic Publishers</publisher> <price>129.95</price> </book> </bib> Example data:list of books

  13. XML Query Examples, Cont. • Query • List books published by Addison-Wesley after 1991, including their year and title. • Result: • <?xml version="1.0" ?> • <result> • <bib> • <book year="1994"> • <title>TCP/IP Illustrated</title> • </book> • <book year="1992"> • <title>Advanced Programming in the Unix environment</title> • </book> • </bib> • </result>

  14. Features of Query Languages • A query has three parts • pattern clause • matches nested elements in the input document and binds variables • filter clause • tests the bound variables • constructor clause • specifies the result in terms of the bound variables • Join operator • Combine data from different portions of documents • Path expressions • Querying without precise knowledge of the document structure • Other useful features: • to check for the absence of information, e.g., missing fields. • Use of arbitrary external functions, such as aggregation functions, string comparison functions, etc. • Use of navigation operators, simplify handling data with references.

  15. XML-QL CONSTRUCT <bib> { WHERE <bib> <book year=$y> <title>$t</title> <publisher><name>Addison-Wesley</name></publisher> </book> </bib> IN "www.bn.com/bib.xml", $y > 1991 CONSTRUCT <book year=$y><title>$t</title></book> } </bib> • patterns and filters appear in the WHERE clause • the constructor appears in the CONSTRUCT clause • The result of the inner WHERE clause is a relation, that maps variables to tuples of values that satisfy the clause • all pairs of year and title values bound to ($y, $t) that satisfy the clause • The result contains one <book> element for each book that satisfies the WHERE clause of the inner query, one for each pair ($y, $t)

  16. YATL make bib [ *book [ @year [ $y ], title [ $t ] ] ] match "www.bn.com/bib.xml" with bib [ *book [ @year [ $y ], title [ $t ] ], publisher [ name [ $n ] ] ] where $n = "Addison-Wesley" and $y > 1991 • the constructor appears in the make clause • patterns appear in the match clause • a bib element may have many book elements, • but that each book element has one year attribute, one publisher element, and one title element • filters appear in the where clause

  17. Lorel select xml(bib:{ (select xml(book:{@year:y, title:t}) from bib.book b, b.title t, b.year y where b.publisher = "Addison-Wesley" and y > 1991)}) • constructor appears in the select clause • patterns appear in the from clause • both patterns and filters appear in the where clause. • bib is used as the entry point for the data in the XML document • The from clause binds variables to the element ids of elements denoted by the given pattern, and the where clause selects those elements that satisfy the given filters • The select clause constructs a new XML book element with a year attribute and a title element.

  18. XQL document("http://www.bn.com")/bib { book[publisher/name="Addison-Wesley" and @year>1991] { @year | title } } • XQL: from the “document world” • The pattern document("http://www.bn.com")/bib • selects all top-level bib elements • evaluates the nested expression for each such element • selects the book elements that are children of a bib element and that satisfy the filter clause in brackets • XQL does not have a constructor clause; the pattern expressions determine the result of the query • the inner-most expression: the book's year attribute and title element

  19. XQuery: An XML Query Language • W3C standard • http://www.w3.org/TR/xquery • Derived from QuiltJonathan Robie, Don Chamberlin, and Daniela Florescu • Based on XML-QL • Relevant W3C documents • XML Query Requirements • XML Query Use Cases • XQuery 1.0: An XML Query Language • XQuery 1.0 and XPath 2.0 Data Model • XQuery 1.0 Formal Semantics • XML Syntax for XQuery 1.0 (XQueryX)

  20. XQuery <bib>{ for $b in //bib/book where $b/publisher = "Addison-Wesley" and $b/@year > 1991 return <book year = {$b/@year}>{ $b/title }</book> }</bib> • Overview • Path expressions: XPath • FLWR (“flower”) expressions • FOR vs. LET expressions • Collections and sorting • Other constructs

  21. XPath • W3C Standard • http://www.w3.org/TR/xpath • Building block for other W3C standards: • XSL Transformations (XSLT) • XML Link (XLink) • XML Pointer (XPointer) • XML Query • Was originally part of XSL

  22. XPath Overview • bib matches a bib element • * matches any element • / matches the root element • /bib matches a bib element under root • bib/paper matches a paper in bib • bib//paper matches a paper in bib, at any depth • //paper matches a paper at any depth • paper|book matches a paper or a book • @price matches a price attribute • bib/book/@price matches price attribute in book, in bib • bib/book/[@price<“55”]/author/lastname

  23. FLWR (“Flower”) Expressions • “Flower” expressions FOR ... LET... FOR... LET... WHERE... RETURN... • Example: find all books titles published after 1995 FOR $x IN document("bib.xml")/bib/book WHERE $x/year > 1995 RETURN $x/title Result: <title>TCP/IP Illustrated</title> <title>Advanced Programming the Unix environment</title> <title>Data on the Web</title> <title>The Economics of Technology and Content …</title>

  24. FLWR (“Flower”) Expressions, Cont. FOR/LET Clauses List of tuples WHERE Clause List of tuples RETURN Clause Instance of XQuery data model • FOR $x in expr • binds $x to each element in the list expr • LET $x = expr • binds $x to the entire list expr • Useful for common subexpressions and for aggregations

  25. FOR vs. LET • FOR Query FOR $x IN document("bib.xml")/bib/book RETURN <result> $x </result> • Returns <result> <book>...</book></result> <result> <book>...</book></result> <result> <book>...</book></result> • LET Query LET $x:=document("bib.xml")/bib/book RETURN <result> $x </result> • Returns <result> <book>...</book> <book>...</book> <book>...</book> ... </result>

  26. More Complex FLWR Expressions • For each author of a book by Morgan Kaufmann, list all his/her books: FOR $a IN distinct(document("bib.xml")/bib/book[publisher=“Morgan Kaufmann”]/author) RETURN <result> $a, FOR $t IN /bib/book[author=$a]/title RETURN $t </result> (distinct: eliminates duplicates) • Find books whose price is larger than average: LET $a=avg(document("bib.xml")/bib/book/@price) FOR $b in document("bib.xml")/bib/book WHERE $b/@price > $a RETURN $b

  27. Collections in XQuery • Ordered and unordered collections • Ordered collection • /bib/book/author • Unordered collection • distinct(/bib/book/author) • LET $a = /bib/book$a is a collection • $b/author a collection (several authors...) • $b/@pricelist of n prices • $b/@price * 0.7 list of n numbers • $b/@price * $b/@quantity list of n x m numbers

  28. Sorting in XQuery <publisher_list> FOR $p IN distinct(document("bib.xml")//publisher) RETURN <publisher> <name> $p/text() </name> , FOR $b IN document("bib.xml")//book[publisher = $p] RETURN <book> $b/title , $b/@price </book> SORTBY(price DESCENDING) </publisher> SORTBY(name) </publisher_list> • Sorting arguments • Refer to the name space of the RETURN clause, not the FOR clause • To sort on an element you don’t want to display • Return it, then remove it with an additional query.

  29. If-Then-Else FOR $h IN //holding RETURN <holding> $h/title, IF $h/@type = "Journal" THEN $h/editor ELSE $h/author </holding> SORTBY (title)

  30. Existential Quantifiers FOR $b IN //book WHERE SOME $p IN $b//para SATISFIES contains($p, "sailing") AND contains($p, "windsurfing") RETURN $b/title FOR $b IN //book WHERE EVERY $p IN $b//para SATISFIES contains($p, "sailing") RETURN $b/title

  31. Other Constructs • BEFORE and AFTER • for dealing with order in the input • FILTER • deletes some edges in the result tree • Recursive functions • Currently: arbitrary recursion • Perhaps more restrictions in the future?

  32. XQueryX LET $authors := /book/author RETURN <AUTHORS>{ $authors }</AUTHORS> <q:query xmlns:q="http://www.w3.org/2001/06/xqueryx"> <q:flwr> <q:letAssignment variable="$authors"> <q:step axis="CHILD"> <q:identifier/> <q:step axis="CHILD"> <q:identifier>book</q:identifier><q:identifier>author</q:identifier> </q:step> </q:step> </q:letAssignment> <q:return> <q:elementConstructor> <q:tagName><q:identifier>AUTHORS</q:identifier></q:tagName> <q:variable>$authors</q:variable> </q:elementConstructor> </q:return> </q:flwr> </q:query>

  33. XQuery Software • QuiP • http://www.softwareag.com/developer/downloads/default.htm • Software AG • Windows and Linux on x86 • Features • Latest W3C syntax • Graphical user interface. • Kweelt • http://kweelt.sourceforge.net/ • Open Source • Runs on all Java platforms • Problems • Older syntax, from previous W3C requirements. • No graphical user interface.

  34. Example Application: Cruise Controller • Vehicle cruise controller. • Modelled with a process graph of 32 processes. • Mapped on 5 nodes: CEM, ABS, ETM, ECM, TCM.

  35. Schedule Table P1 P4 24 ms P3 P2 m3 m4 P1 S1 S0 m1 m2 Round 1 Round 2 Round 3 Round 4 Round 5 m1 m2 P2 P3 m3 m4 P4

  36. XML Model of the Cruise Controller • architecture.xml <NODE Name="CEM" Id="P1"> <Processor Name="AMD"><P_Type>I</P_Type></Processor> <Memory unit="KB">128</Memory> </NODE> • behaviour.xml <PROCESS Name="PR3" Id="PR3"> <WCET unit="ms">7</WCET><Memory unit="KB">2</Memory> </PROCESS> <ARC Name="ARC3" Id="ARC3"> <Src>PR3</Src><Dest>PR4</Dest><Delay unit="ms">0</Delay> </ARC> • mapping.xml <MAP Resource="P1"> <Process>PR1</Process><Process>PR2</Process><Process>PR30</Process> </MAP> • schedule.xml <SLOT Id="PR1"><Start unit="ms">0</Start><Duration unit="ms">0</Duration> <Resource>P6</Resource></SLOT> <SLOT Id="PR2"><Start unit="ms">0</Start><Duration unit="ms">12</Duration> <Resource>P1</Resource></SLOT>

  37. Requirements on the Cruise Controller • Requirements on the model • The model should be consistent • Every process should be mapped to one and only one node • Every sensor/actuator should be connected • The schedule should be correct • The schedule should respect the precedence constraints • No two slots in the schedule should overlap • Cruise Controller • Timing requirements • The CC should execute within 100 ms • Resource requirements • The sum of processes’ memory on a nodeshould not exceed that node's capacity • Should be expressed in XQuery!

  38. Resource Requirements: Query The sum of processes’ memory on a node should not exceed that node's capacity for $map in document("data/sweb/mapping.xml")//MAP, $nod in document("data/sweb/architecture.xml")//:NODE[@Id = $map/@Resource] let $proc := document("data/sweb/behaviour.xml")//PROCESS[@Id = $map/Process] return <processor Name={$nod/@Name} Id={$nod/@Id} HasMemory={$nod/Memory/text(),$nod/Memory/@unit} MemoryUsedByScheduledProcesses={sum($proc/Memory),$nod/Memory/@unit}> { for $process in $proc return <process Name={$process/@Name} Id={$process/@Id} Memory={$process/Memory/text(),$process/Memory/@unit} /> sortby(int(substring-before(@Memory,"K"))) } </processor> sortby(int(substring-after(@Id,"P")))

  39. Resource Requirements: Result query result:check_resource_consistency.xml <?xml version="1.0" ?> <quip:result xmlns:quip="http://.."> <processor Name="CEM" Id="P1" HasMemory="128KB" MemoryUsedByScheduledProcesses="20KB"> <processName="PR1" Id="PR1" Memory="1KB" /> <processName="PR31" Id="PR31" Memory="4KB" /> <processName="PR30" Id="PR30" Memory="5KB" /> <processName="PR2" Id="PR2" Memory="10KB" /> </processor> <processor Name="ABS" Id="P2" HasMemory="256KB" MemoryUsedByScheduledProcesses="25KB"> <processName="PR32" Id="PR32" Memory="1KB" /> <processName="PR27" Id="PR27" Memory="2KB" /> <processName="PR3" Id="PR3" Memory="2KB" /> <processName="PR4" Id="PR4" Memory="5KB" /> <processName="PR29" Id="PR29" Memory="7KB" /> <processName="PR28" Id="PR28" Memory="8KB" /> </processor> <processor Name="ETM" Id="P3" HasMemory="128KB“ MemoryUsedByScheduledProcesses="40KB"> <processName="PR14" Id="PR14" Memory="2KB" /> <processName="PR11" Id="PR11" Memory="2KB" /> … </processor> … </quip:result>

  40. Use Case “XMP”: Experiences and Exemplars xmp-data.xml XMPQ1.xquery <bib> <book year="1994"> <title>TCP/IP Illustrated</title> <author><last>Stevens</last> <first>W.</first></author> <publisher>Addison-Wesley</publisher> <price>65.95</price> </book> <book year="1992"> <title>Advanced Prog… the Unix environment</title> <author><last>Stevens</last><first>W.</first> </author> <publisher>Addison-Wesley</publisher> <price>65.95</price> </book> <book year="2000"> <title>Data on the Web</title> <author><last>Abiteboul</last><first>Serge</first></author> <author><last>Buneman</last><first>Peter</first></author> <author><last>Suciu</last><first>Dan</first></author> <publisher>Morgan Kaufmann Publishers</publisher> <price>39.95</price> </book>- <book year="1999"> <title>The Economics of Technology and Content for Digital TV</title> <editor><last>Gerbarg</last><first>Darcy</first> <affiliation>CITI</affiliation> </editor> <publisher>Kluwer Academic Publishers</publisher> <price>129.95</price> </book> </bib> <bib>{ for $b in document("data/xmp-data.xml")/bib/book where $b/publisher = "Addison-Wesley" and int($b/@year) > 1991 return <book year = {$b/@year}>{ $b/title }</book> }</bib>

  41. Use Case “XMP”: Experiences and Exemplars Result of: List books published by Addison-Wesley after 1991, including their year and title. <?xml version="1.0" ?> <quip:result xmlns:quip="http://namespaces.softwareag.com/tamino/quip/"> <bib> <book year="1994"> <title>TCP/IP Illustrated</title> </book> <book year="1992"> <title>Advanced Programming in the Unix environment</title> </book> </bib> </quip:result>

  42. Use Case “TREE”: Qs that preserve hierarchy tree-data.xml TREEQ2.xquery <?xml version="1.0" ?> <!DOCTYPE bookSYSTEM “book.dtd”> <book> <title>Data on the Web</title> <author>Serge Abiteboul</author> <author>Peter Buneman</author> <author>Dan Suciu</author> <section id="intro" difficulty="easy"> <title>Introduction</title> <p>Text ...</p> <section> <title>Audience</title> <p>Text ...</p> </section> <section> <title>Web Data and the Two Cultures</title> <p>Text ...</p> <figure height="400" width="400"> <title>Traditional client/server architecture</title> <imagesource="csarch.gif" /> </figure> <p>Text ...</p> </section> </section> <section id="syntax" difficulty="medium"> …. </section> …. </book> <figlist>{ for $f in document("data/tree-data.xml")//figure return <figure>{ ($f/@* ,$f/title ) }</figure> }</figlist>

  43. Use Case “TREE”: Qs that preserve hierarchy Result of: Prepare a (flat) figure list for first book, listing all the figures and their titles. Preserve the original attributes of each <figure> element, if any. <?xml version="1.0" ?> <quip:result xmlns:quip="http://namespaces.softwareag.com/tamino/quip/"> <figlist> <figure height="400" width="400"> <title>Traditional client/server architecture</title> </figure> <figure height="200" width="500"> <title>Graph representations of structures</title> </figure> <figure height="250" width="400"> <title>Examples of Relations</title> </figure> </figlist> </quip:result>

  44. Use Case “TREE”: Qs that preserve hierarchy TREEQ3.xquery/Result TREEQ4.xquery/Result (<section_count>{ count(document("data/tree-data.xml")//section) }</section_count> ,<figure_count>{ count(document("data/tree-data.xml")//figure) }</figure_count> ) <?xml version="1.0" ?>- <quip:result xmlns:quip="http://namespaces. softwareag.com/tamino/quip/"> <section_count>7</section_count> <figure_count>3</figure_count> </quip:result> <top_section_count>{ count(document("data/tree-data.xml")/book/section) }</top_section_count> <?xml version="1.0" ?> <quip:result xmlns:quip="http://namespaces. softwareag.com/tamino/quip/"><top_section_count>2</top_section_count> </quip:result>

  45. Use Case “SEQ”: Queries based on sequence report1.xml SEQQ2.xquery report> <section> <section.title>Procedure</section.title> <section.content>The patient was taken to the operating room where she was placed in supine position and <anesthesia>induced under general anesthesia.</anesthesia> <prep> <action>A Foley catheter was placed to decompress the bladder </action> and the abdomen was then prepped and draped in sterile fashion. </prep> <incision>A curvilinear incision was made <geography>in the midline immediately infraumbilical </geography> and the subcutaneous tissue was divided <instrument>using electrocautery.</instrument> </incision> The fascia was identified and <action>#2 0 Maxon stay sutures were placed on each side of the midline. </action> <incision>The fascia was divided using <instrument>electrocautery</instrument> and the peritoneum was entered. </incision> … </section.content> </section> </report> for $s in document("data/report1.xml")//section[section.title = "Procedure"] let $instruments := $s//instrument for $i in 1 to 2 return $instruments[$i] Result of: In the Procedure section of Report1, what are the first two Instruments to be used? <?xml version="1.0" ?> <quip:result xmlns:quip="http://namespaces. softwareag.com/tamino/quip/"> <instrument>using electrocautery. </instrument> <instrument>electrocautery</instrument> </quip:result>

  46. Use Case “R”: Access to Relational Data relational data RQ2.xquery USERS USERID NAME RATING U01 Tom Jones B U02 Mary Doe A U03 Dee Linquent D U04 Roger Smith C U05 Jack Sprat B U06 Rip Van Winkle B ITEMS ITEMNO DESCR O_BY DATE PRICE 1001 Red Bicycle U01 99-01-05 99-01-20 40 1002 Motorcycle U02 99-02-11 99-03-15 500 1003 Old Bicycle U02 99-01-10 99-02-20 25 1004 Tricycle U01 99-02-25 99-03-08 15 1005 Tennis Racket U03 99-03-19 99-04-30 20 1006 Helicopter U03 99-05-05 99-05-25 50000 1007 Racing Bicycle U04 99-01-20 99-02-20 200 1008 Broken Bicycle U01 99-02-05 99-03-06 25 BIDS USERID ITEMNO BID BID_DATE U02 1001 35 99-01-07 U04 1001 40 99-01-08 U02 1001 45 99-01-11 U04 1001 50 99-01-13 U02 1001 55 99-01-15 U01 1002 400 99-02-14 …. <result> { for $u in document("users.xml")//user_tuple for $i in document("items.xml")//item_tuple where $u/rating > "C" and $i/reserve_price > 1000 and $i/offered_by = $u/userid return <warning> { $u/name } { $u/rating } { $i/description } { $i/reserve_price } </warning> } </result>

  47. Use Case “R”: Access to Relational Data Result of: Find cases where a user with a rating worse (alphabetically, greater) than "C" is offering an item with a reserve price of more than 1000. <?xml version="1.0" ?> - <quip:result …> <result>- <warning> <name>Dee Linquent</name> <rating>D</rating> <description>Helicopter</description> <reserve_price>50000</reserve_price> </warning> </result> </quip:result>

  48. Use Case “R”: Access to Relational Data Result of: List names of users who have placed multiple bids of at least $100 each. <result>{ for $u in document("data/R-users.xml")//user_tuple let $b := document("data/R-bids.xml")//bid_tuple[userid = $u/userid and int(string-value(bid)) >= 100] where count($b) > 1 return <big_spender>{ $u/name/text() }</big_spender> }</result> Result: <?xml version="1.0" ?> <quip:result xmlns:quip="http://namespaces.softwareag.com/tamino/quip/"> <result> <big_spender>Mary Doe</big_spender> <big_spender>Dee Linquent</big_spender> <big_spender>Roger Smith</big_spender> </result> </quip:result>

  49. Use Case “PARTS”: Recursive Parts Explosion parts-data.xml PARTSQ1a.xquery <?xml version="1.0" encoding="ISO-8859-1" ?> partlist> <partpartid="0" name="car" /> <partpartid="1" partof="0" name="engine" /> <partpartid="2" partof="0" name="door" /> <partpartid="3" partof="1" name="piston" /> <partpartid="4" partof="2" name="window" /> <partpartid="5" partof="2" name="lock" /> <partpartid="10" name="skateboard" /> <partpartid="11" partof="10" name="board" /> <partpartid="12" partof="10" name="wheel" /> <partpartid="20" name="canoe" /> </partlist> define function one_level(xs:AnyType $p, xs:AnyType $ps) returns xs:AnyType { <part>{ ($p/@partid ,$p/@name ,for $s in $ps[$p/@partid = @partof] return one_level($s,$ps) ) }</part> } let $ps := document("data/parts-data.xml")/partlist/part for $p in $ps[not(@partof)] return one_level($p,$ps)

  50. Use Case “PARTS”: Recursive Parts Explosion Result of: Convert the sample document from "partlist" format to "parttree" format (see DTD section for definitions). In the result document, part containment is represented by containment of one <part> element inside another. Each part that is not part of any other part should appear as a separate top-level element in the output document. <?xml version="1.0" ?> - <quip:result xmlns:quip="http://namespaces.softwareag.com/tamino/quip/"> <part partid="0" name="car"> <part partid="1" name="engine"> <partpartid="3" name="piston" /> </part> <part partid="2" name="door"> <partpartid="4" name="window" /> <partpartid="5" name="lock" /> </part> </part> <part partid="10" name="skateboard"> <partpartid="11" name="board" /> <partpartid="12" name="wheel" /> </part> <partpartid="20" name="canoe" /> </quip:result>

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