1 xquery informationssysteme, 14.06.2007 vortragender: michael schmidt

1

XQuery

Informationssysteme, 14.06.2007

Vortragender: Michael Schmidt

2

XPath (Wiederholung)

Anfragesprache auf XML XPath-Expressions selektieren Knoten des

Eingabe-Dokuments

bib

book book

title titleauthor author

/bib//title

3

XPath (Wiederholung)

Path Steps: axis::nodetest Axen: „child“, „descendant“, „ancestor“,

„following“, „following-sibling“, ... Node-tests: Tag, „*“, „node()“, „text()“

Absolute Pfade: /step/step/… Relative Pfade: step/step/...

4

XQuery

„SQL für XML“ W3C Recommendation Funktionale Programmiersprache,

Turing-vollständig XQueries enthalten XPath Ausdrücke Ergebnis einer XQuery: wohlgeformte XML-

Dokumente (XPath: Menge von Knoten) Keine Datenmanipulationssprache (z.B. keine

Updates)

5

Node-Construction und Konstanten

<result> <text>{ "Hello World" }</text></result>

XQuery

<result> <text>Hello World</text></result>

Ergebnis

<result> <text>"Hello World"</text></result>

XQuery

<result> <text>"Hello World"</text></result>

Ergebnis

6

Dokument-Zugriff

<books> { doc("bookstore.xml")/bib/book[price>30]} </books>

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<books> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> </books>

Ergebnis

XQuery

7

Sequenz

<titles> { ( doc("bookstore.xml")/bib/article/title, doc("bookstore.xml")/bib/book/title )} </titles>

<titles> <title>T3</title> <title>T1</title> <title>T2</title></titles>

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

Ergebnis

XQuery

Ordnung bleibt erhalten!

8

FR-Expression

<booktitles> { for $book in doc("bookstore.xml")//book return $book/title} </booktitles>

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> <title>T1</title> <title>T2</title></booktitles>

Ergebnis

XQuery

9

FWR-Expressions<booktitles> { for $book in doc("bookstore.xml")//book where $book/price>30 return <booktitle>{ $book/title/text() }</booktitle>} </booktitles>

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> <booktitle>T1</booktitle></booktitles>

Ergebnis

Konstruktion von Knoten, die im Dokument nicht

vorkommen

XQuery

10

FLWR-Expressions<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> { for $book in doc("bookstore.xml")//book let $booktitle := <bt>{ $book/title/text() }</bt> where ($book/price>30) return $booktitle} </booktitles>

<booktitles> <bt>T1</bt></booktitles>

Ergebnis

XQuery

11

FLWOR-Expressions

<booktitles> { for $book in doc("bookstore.xml")//book let $booktitle := $book/title where ($book/price>10) order by $booktitle/text() descending return <bt>{ $booktitle/text() }</bt>} </booktitles>

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> <bt>T2</bt> <bt>T1</bt></booktitles>

Ergebnis

XQuery

12

Where-Expressions

Konnektive and, or, fn:not

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> { for $book in doc("bookstore.xml")//book where ($book/price>10 and

fn:not($book/author/text()="A1")) return $book/title} </booktitles>

<booktitles> <title>T2</title></booktitles>

Ergebnis

XQuery

13

Some-Expressions

bookstore.xml

<booktitles> { for $book in doc("bookstore.xml")//book where (some $a in $book/author satisfies $a/text()="A2") return $book/title} </booktitles>

Ergebnis

XQuery

<bib> <book> <title>T1</title> <author>A1</author> <author>A2</author> </book> <book> <title>T2</title> <author>A3</author> <author>A4</author> </book></bib>

<booktitles> <title>T1</title></booktitles>

14

For vs let-Expressions

<for>{ for $x in (1 to 5) return <test> {$x} </test>}</for>

<let>{ let $x:=(1 to 5) return <test> {$x} </test>}</let>

<for> <test>1</test> <test>2</test> <test>3</test> <test>4</test> <test>5</test></for>

XQuery 1

XQuery 2

Ergebnis

Iteration

keine Iteration<let> <test>1 2 3 4 5</test></let>

Ergebnis

15

If-then-else Expressions

<booktitles> { for $book in doc("bookstore.xml")//book return if (fn:exists($book/price)) then <priced>{ $book/title }</priced> else <unpriced>{ $book/title }</unpriced>} </booktitles>

XQuery bookstore.xml

<bib> <book> <title>T1</title> <author>A1</author> </book> <book> <title>T2</title> <author>A2</author> <price>30</price> </book></bib>

<booktitles> <unpriced><title>T1</title></unpriced> <priced><title>T2</title></priced></booktitles>

Ergebnis

16

Vordefinierte Funktionen

Zahlreiche built-in Functions: Boolean: fn:exists(), fn:empty() … String Manipulation: fn:concat(), fn:uppercase() … String Tests: fn:contains(), fn:starts-with() … Sequenzen: fn:exactly-one(), fn:distinct-values() … Mathematisch: fn:floor(), fn:round(), fn:abs() …

…

17

Vordefinierte Funktionen

<booktitles> { for $book in doc("bookstore.xml")//book where (fn:exists($book/price) and fn:contains($book/author, "A")) return $book/title} </booktitles>

XQuery

<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<booktitles> <title>T1</title> <title>T2</title></booktitles>

Ergebnis

18

XQuery Joins

Vergleich unterschiedlicher Teile des Eingabe-Dokuments

Auch Joins zwischen verschiedenen Dokumenten möglich

Im Gegensatz zu SQL-Joins, oftmals nicht leicht zu erkennen, da keine eigene Syntax (kein JOIN-Keyword)

Optimierung der Auswertung von Joins durch herkömmliche und XML-spezifische Methoden

19

XQuery Joins<titles> { for $bib in doc("bookstore.xml")/bib return for $book in $bib/book return for $article in $bib/article where $book/author=$article/author return <pair>{ $book/title, $article/title}</pair>} </titles>

XQuery

bib

book

title author

T1 A1

book

title author

T2 A2

article

title author

T3 A3

article

title author

T4 A1

$book $article

<titles> <pair> <title>T1</title> <title>T4</title> </pair></titles>

Ergebnis

20

XQuery Joins

<books-with-prices> {

for $a in doc("www.amazon.com/review.xml")//book

for $b in doc("www.bn.com/bib.xml")//entry

where $a/isbn = $b/isbn

return

<book-with-prices>

{ $b/title }

<amazon> { $a/price/text() } </amazon>

<bn> { $b/price/text() } </bn>

</book-with-prices>

} </books-with-prices>

XQuery

Join über zwei Dokumente

21

Aggregatfunktionen

fn:min(), fn:max(), fn:count(), fn:sum(), fn:avg()

<booktitles> {

for $book in doc("bookstore.xml")//book return { ($book/title, <authors>{ fn:count($book/author) }</authors>) }} </booktitles>

XQuery bookstore.xml

<bib> <book> <title>T1</title> <author>A1</author> <author>A2</author> </book> <book> <title>T2</title> <author>A3</author> </book></bib>

<booktitles> <title>T1</title><authors>2</authors> <title>T2</title><authors>1</authors></booktitles>

Ergebnis

22

Aggregatfunktionen

<adressliste> { for $o in fn:distinct-values(doc("adressen.xml")//ort) let $ort:=doc("adressen.xml")//ort[self::node()=$o] where fn:count($ort)>=2 order by $o return <ortsliste> <ort>{($ort[1]/name,$ort[1]/plz)}</ort> <anzahl>{count($ort)}</anzahl></ortsliste>} </adressliste>

Beispiel: Gegeben Adressdatenbank, berechne Orte und Zahl der Adressen für Orte mit mind. 2 Adressen

adressen.xml

<adressliste> <adresse> <ort> <name>SB</name> <plz>66121</plz> </ort> <strasse>S1</strasse> </adresse> <adresse> <ort> <name>SB</name> <plz>66121</plz> </ort> <strasse>S2</strasse> </adresse> …</adressliste>

ErgebnisSB66121, NK66538, …

23

Datentransformation

XML: Generalisierung von HTML XQuery ermöglicht Anfragen auf XML-

Dokumente und direkte Ausgabe von HTML

XML und XQuery in Web-Szenarien gut geeignet

24

Datentransformation<bib> <book> <title>T1</title> <author>A1</author> <price>50</price> </book> <book> <title>T2</title> <author>A2</author> <price>20</price> </book> <article> <title>T3</title> <author>A3</author> </article></bib>

bookstore.xml

<html> <head> <title>Angebot</title> </head> <body> <h1>Buchliste</h1> <table border="1">{ for $book in doc("bookstore.xml")//book return <tr> <td><b>{$book/title/text()}</b></td> <td>{$book/author/text()}</td> </tr> }</table> </body></html>

XQuery

25

Datentransformation<html> <head> <title>Angebot</title> </head> <body> <h1>Buchliste</h1> <table border=1> <tr> <td><b>T1</b></td> <td>A1</td> </tr> <tr> <td><b>T2</b></td> <td>A2</td> </tr> </table> </body></html>

Ergebnis

26

Vielfalt an Konstrukten

FLWOR – Expressions Aggregationen Typkonversionen (nicht besprochen) Gleichheit von Knoten (Benutzerdefinierte) Funktionen

Sehr komplex, effiziente Auswertung von XQuery noch immer ein aktives Forschungsgebiet

27

XQ – ein XQuery Fragment

query ::= Ɛ | <a>query</a> | query query

| var | var/axis::v

| for var in var/axis::v return query

| if cond then query else query

cond ::= var = var | var = <a/> | true

| some var in var/axis::v satisfies cond

| cond and cond | cond or cond | not cond

Syntax Composition-free XQ

28

Composition-free XQuery

book

bib

book

<books> { let $x := <booklist>{ for $book in /bib/book return <b>{ $book } </b> }</booklist> for $b in $x/booklist/b return $b/* } </books>

XQuery

29

Composition-free XQuery

book

bib

book book

booklist

book

b b

$x$book

<books> { let $x := <booklist>{ for $book in /bib/book return <b>{ $book } </b> }</booklist> for $b in $x/booklist/b return $b/* } </books>

neu konstruiert

XQuery

30

Composition-free XQuery

book

bib

book book

booklist

book

b b

$x

book

books

book

$book $b

<books> { let $x := <booklist>{ for $book in /bib/book return <b>{ $book } </b> }</booklist> for $b in $x/booklist/b return $b/* } </books>

XQuery

31

Composition-free XQuery

in der Praxis: viele XQuery Anfragen mit Komposition

können in äquivalente XQ-Anfragenumgeschrieben werden

<books> { let $x := <booklist>{ for $book in /bib/book return <b>{ $book } </b> }</booklist> for $b in $x/booklist/b return $b/* } </books>

<books>{

for $book in /bib/book return $book

}</books>

XQuery

XQ query

32

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

x

x

y y

$x

r

Ergebnis

<r>

XQ expression

33

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

x

x

y y

$x

$y

r

Ergebnis

<r><y/>

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

XQ expression

34

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

x

x

y y

$x

$y

r

Ergebnis

<r><y/><y/>

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

XQ expression

35

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

x

x

y y

$x

r

Ergebnis

<r><y/><y/>

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

XQ expression

36

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

x

x

y y$y

r

$x

Ergebnis

<r><y/><y/><y/>

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

XQ expression

37

Eigenschaft von XQ

niedrigere Komplexität in der Auswertung

Variablen binden immer an einen Knoten im Eingabebaum

x

x

y y

r

$x

$y

<r><y/><y/><y/><y/><r/>

Ergebnis

<r>{

for $x in //x return

for $y in $x//y return $y}</r>

XQ expression

38

XQ formale Semantik

k: Anzahl gebundener Variablen

e: derzeitiges environment (Variablenbindung)

“false” als leere Liste

Ergebnis: Liste von Knoten

39

XQ formale Semantik

40

XQ formale Semantik

41

XQ Evaluierung

[[<r>{ $x2 $x1}</r>]]2 (<a/>,<b/>)

= [<r> [[$x2 $x1]]2 (<a/>,<b/>) </r>]

= [<r> [[$x2]]2 (<a/>,<b/>) [[$x1]]2 (<a/>,<b/>) </r>]

= [<r> <b/> <a/> </r>]

42

XQ Evaluierung

<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>

bookstore.xml

<bib> <book> <title>T1</title> <author>A1</author> </book> <book> <title>T2</title> <author>A2</author> </book></bib>

XQuery

43

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

44

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

45

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

46

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)

47

XQ Evaluierung

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>)

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)

48

XQ Evaluierung

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A1</author><title>T1</title></book>)

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>)

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)

49

XQ Evaluierung

l =[[$book/author]]1 (<book><author>A1</author> <title>T1</title></book>) =[<author>A1</author>]

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A1</author><title>T1</title></book>)

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l2) + [[if (some …)]]1 (l1)

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>)

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A1</author>)

50

XQ Evaluierung

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A1</author>) [<yes/>]

l =[[$book/author]]1 (<book><author>A1</author> <title>T1</title></book>) =[<author>A1</author>]

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A1</author><title>T1</title></book>)

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>)

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)

[[$author/text()]]2 (…) [“A1”]

[[“A1”]]2 (…) [“A1”]

51

XQ Evaluierung

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A1</author>) [<yes/>]

l =[[$book/author]]1 (<book><author>A1</author> <title>T1</title></book>) =[<author>A1</author>]

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A1</author><title>T1</title></book>) [<yes/>]

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>)

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)

52

XQ Evaluierung

[[$book]]1

(<book><author>A1</author><title>T1</title></book>)

[<book><author>A1</author><title>T1</title></book>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A1</author>) [<yes/>]

l =[[$book/author]]1 (<book><author>A1</author> <title>T1</title></book>) =[<author>A1</author>]

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A1</author><title>T1</title></book>) [<yes/>][[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A1</author><title>T1</title></book>) [<book><author>A1</author><title>T1</title></book>]

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

53

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>)

54

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 ()= [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l0) + [[if (some …)]]1 (l1)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>)

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>)

55

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 ()= [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>)

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>)

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>)

56

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>)

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>)

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>) []

[[$author/text()]]2 (…) [“A2”]

[[“A1”]]2 (…) [“A1”]

57

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>)

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>) []

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>) []

58

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 ()

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] +

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>) []

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>) []

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>) []

[[()]]1 (<book><author>A2</author><title>T2</title</book>) []

[]

59

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 ()

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 () [<book><author>A1</author><title>T1</title></book>]

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] + []

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>) []

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>) []

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>) []

[[()]]1 (<book><author>A2</author><title>T2</title</book>) []

60

XQ Evaluierung

[[<bt>{ for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()}</bt>]]0 () [<bt><book><author>A1</author><title>T1</title></book></bt>]

[[for $book in //book return if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]0 () [<book><author>A1</author><title>T1</title></book>]

l=[[//book]]0 () = [<book><author>A1</author><title>T1</title></book>,

<book><author>A2</author><title>T2</title></book>]

[[if (some …)]]1 (l1) + [[if (some …)]]1 (l2)[<book><author>A1</author><title>T1</title></book>] + []

[[if (some $author in $book/author satisfies $author/text()=“A1”) then $book else ()]]1

(<book><author>A2</author><title>T2</title></book>) []

[[for $author in $book/author return $author/text()=“A1”]]1 (<book><author>A2</author><title>T2</title></book>) []

l =[[$book/author]]1 (<book><author>A2</author> <title>T2</title></book>) =[<author>A2</author>]

[[$author/text()=“A1”]]2

(<book>…</book>, <author>A2</author>) []

[[()]]1 (<book><author>A2</author><title>T2</title</book>) []

61

XQ: 2 Arten von Gleichheit Deep Equality

Vergleiche Bäume als Werte

z.B.: n1 deep-equal n2

n2 deep-equal n7 n3 =deep-equal n10

n4 =deep-equal n11

n4 deep-equal n10

Atomic EqualityVergleiche Blätter als Werte

z.B.: n4 =atomic n11

n4 atomic n9

n1: people

n2: person

n4: Karl n6: Auer

n7: person

n5: lnn3: fn

n9: Auer n11: Karl

n10: fnn8: ln

62

XQuery – Komplexere Beispiele

<bib> { for $b in doc("doc.xml")//book where fn:count($b/author) > 0 return <book> { $b/title } { for $a in $b/author[position()<=2] return $a } { if (fn:count($b/author) > 2) then <et-al/> else () } </book>} </bib>

Für jedes Buch mit mindestens einem Autor, gib den Titel und die ersten beiden Autoren aus und ein leeres „et-al“-Element wenn das Buch weitere Autoren besitzt

XQuery

63

XQuery – Komplexere BeispieleFinde den minimalen Preis für jedes Buch und gib ihn in der Form eines „minprice“-Elements mit dem Titel des Buchs als „title“-Attribut aus.

<results> { let $doc := doc("doc.xml") for $t in fn:distinct-values($doc//book/title) let $p := $doc//book[title = $t]/price return <minprice title="{ $t }"> <price>{ fn:min($p) }</price> </minprice>} </results>

XQuery

64

XQuery – Komplexere BeispieleGib alle Paare von Büchern aus, die unterschiedliche Titel aber die

selben Autoren (möglicherweise in unterschiedlicher Reihenfolge) haben.

<bib> { for $book1 in doc("doc.xml")//book, $book2 in doc("doc.xml")//book let $aut1:=for $a in $book1/author order by $a/last, $a/first return $a let $aut2 := for $a in $book2/author order by $a/last, $a/first return $a where $book1 << $book2 and not($book1/title = $book2/title) and fn:deep-equal($aut1, $aut2) return <book-pair> { $book1/title } { $book2/title } </book-pair>} </bib>

XQuery

Annahme:

Autoren haben die Form

<author>

<first>FIRSTNAME</first>

<last>LASTNAME</last>

</author><<: „vor“

65

Literatur und Links

Buch „XQuery from the Experts“, Addison Wesley (Kapitel 1)(Howard Katz, Don Chamberlin, Denise Draper, Mary Fernandez, Michael Kay, Jonathan Robie, Michael Rys, Jerome Simeon, Jim Tivy, Philip Wadler)http://www.datadirect.com/developer/xml/xquery/docs/katz_c01.pdf

XQuery Tutorial:http://www.w3schools.com/xquery/default.asp

W3C XQuery:http://www.w3.org/TR/2007/REC-xquery-20070123/

W3C XQuery Functions: http://www.w3.org/TR/xpath-functions/

Galax XQuery Engine (installiert in CIP-Pools):http://www.galaxquery.org/