xquery introduction by examples. sources xquery 1.0: an xml query languagew3c working draft 22...

Xquery

Introduction by Examples

Sources

• XQuery 1.0: An XML Query LanguageW3C Working Draft 22 August 2003

• Don Chamberlin’s Sigmod03 talk:

www.almaden.ibm.com/cs/people/chamberlin/ sigmod03_xquery.pdf

• Xquery from the Experts. Katz et. Al. • Definitive XML Schema. Priscilla Walmsley.

Example of an Input ExpressionThis is “onebook.xml”:

<?xml version="1.0" encoding="ISO-8859-1"?><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></bib>

Expression and Result

Expression: document("onebook.xml")Result:document { <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></bib>}

Bibliography Database<?xml version="1.0" encoding="ISO-8859-1"?><bib>

<book year="1994"><title>TCP/IP Illustrated</title><author>



</book><book year="1992">

<title>Advanced Programming in the Unix environment</title><author>



</book>

Bibliography Database<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>

Bibliography Database<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>

Some Path Expressions

Expression: document("xmpbib.xml")//book[2]

Result<book year="1992">

<title>Advanced Programming in the Unix environment</title> <author><last>Stevens</last><first>W.</first></author> <publisher>Addison-Wesley</publisher> <price>65.95</price>

</book>

Node Creation

Expression:<book>

<title> Go West </title> <author> J. Cowen </author> <publisher> Smith </publisher>

</book>Result:

<book> <title> Go West </title> <author> J. Cowen </author> <publisher> Smith </publisher>

</book>

Element Creation - Constructor

Expression:

element title { "Harold and the purple crayon" }

Result:

<title>Harold and the purple crayon</title>

Element Creation - Constructor

Expression:

element {concat("tit","le")} { "Harold and the purple crayon" }

Result:

<title>Harold and the purple crayon</title>

Document CreationExpression:document{<book> <title> Go West </title> <author> J. Cowen </author> <publisher> Smith </publisher></book>}Result:

document { <book> <title> Go West </title> <author> J. Cowen </author> <publisher> Smith </publisher> </book>}

Node Creation - Computation

Expression:<example>

<p> here is a query </p> <eg> document("b.xml")//book[1]/title </eg> <eq> { document("../docs/xmpbib.xml")//book[1]/title } </eq>

</example>Result:

<example> <p> here is a query </p> <eg> document("b.xml")//book[1]/title </eg> <eq><title>TCP/IP Illustrated</title></eq></example>

FLWOR

for $b in document("../docs/xmpbib.xml")//book where $b/@year = "2000" return $b/title

Result:

<title>Data on the Web</title>

FLWORfor $i in (1,2,3)

return

<tuple>

<i>

{$i}

</i>

</tuple>Result:

<tuple><i>1</i></tuple>, <tuple><i>2</i></tuple>, <tuple><i>3</i></tuple>

Let

let $i := (1,2,3)return <tuple> <i> {$i} </i> </tuple>Result:<tuple><i>1 2 3</i></tuple>

Tuple Stream Productionfor $i in (1,2,3), $j in (4,5,6)

return

<tuple>

<i>

{$i}

</i>

<j>

{$j}

</j>

</tuple>

Result:next slide

Result of Tuple Stream Production

<tuple><i>1</i><j>4</j></tuple>,








<tuple><i>3</i><j>6</j></tuple>

Tuple Stream Productionfor $i in (1,2,3)let $j := (1,2,3)return <tuple> <i> {$i} </i> <j> {$j} </j> </tuple>

Result:<tuple><i>1</i><j>1 2 3</j></tuple>,<tuple><i>2</i><j>1 2 3</j></tuple>,<tuple><i>3</i><j>1 2 3</j></tuple>

FLWOR + Let for $b in document("../docs/xmpbib.xml")//book

let $c := $b/author

return

<book>

{ $b/title,

<count>

{ count($c) }

</count>

}

</book>

Result: Next slide

Result: FLWOR + Let<book><title>TCP/IP

Illustrated</title><count>1</count></book>,<book> <title>Advanced Programming in the Unix

environment</title> <count>1</count></book>,<book><title>Data on the

Web</title><count>3</count></book>,<book> <title>The Economics of Technology and Content for

Digital TV</title> <count>0</count></book>

More FLWOR for $b in document("../docs/xmpbib.xml")//book

where $b/price < 50

return $b/title

Result:


More FLWOR – Let + Count for $b in document("../docs/xmpbib.xml")//book

let $c := $b//author

where count($c) > 2

return $b/title

Result:


More FLWOR – Order for $t in document("../docs/xmpbib.xml")//title

order by $t

return $t

Result:

<title>Advanced Programming in the Unix environment</title>,

<title>Data on the Web</title>,

<title>TCP/IP Illustrated</title>,

<title>The Economics of Technology and Content for Digital TV</title>

More FLWOR – Variable Binding

for $b in document("../docs/xmpbib.xml")//book, $t in $b/title

order by $t return $tResult:<title>Advanced Programming in the Unix environment</title>,

<title>Data on the Web</title>,<title>TCP/IP Illustrated</title>,<title>The Economics of Technology and Content for Digital TV</title>

Order Specification

for $b in document("../docs/xmpbib.xml")//book, $a in $b/author

order by $a/last descending , $a/first ascending

return $a

Result:<author><last>Suciu</last><first>Dan</first></author>,

<author><last>Stevens</last><first>W.</first></author>,


<author><last>Buneman</last><first>Peter</first></author>,

<author><last>Abiteboul</last><first>Serge</first></author>

Ordering without Outputting

let $b := document("../docs/xmpbib.xml")//book for $t in distinct-values($b/title) let $a1 := $b[title = $t]/author[1] order by $a1/last , $a1/first return $tResult:<title>Data on the Web</title>,<title>TCP/IP Illustrated</title>,<title>Advanced Programming in the Unix environment</title>,<title>The Economics of Technology and Content for Digital

TV</title>

Order Specification – Empty sequences

let $b := document("../docs/xmpbib.xml")//book for $t in distinct-values($b/title) let $a1 := $b[title = $t]/author[1] stable order by $a1/last empty least, $a1/first

empty least return $tResult:<title>The Economics of Technology and Content for Digital TV</title>,<title>Data on the Web</title>,<title>TCP/IP Illustrated</title>,<title>Advanced Programming in the Unix environment</title>

Using FLWOR to Bind a Variable

let $authors := for $a in document("../docs/xmpbib.xml")//author

order by $a/last empty least , $a/first empty least

return $a return $authorsResult:<author><last>Abiteboul</last><first>Serge</first></author>,<author><last>Buneman</last><first>Peter</first></author>,<author><last>Stevens</last><first>W.</first></author>,<author><last>Stevens</last><first>W.</first></author>,<author><last>Suciu</last><first>Dan</first></author>

Using FLWOR to Bind a Variable

(<author><last>Abiteboul</last><first>Serge</first></author>,




<author><last>Suciu</last><first>Dan</first></author> ) /last

Result:<last>Abiteboul</last>,

<last>Buneman</last>,

<last>Stevens</last>,


<last>Suciu</last>

A Bug?

let $authors := for $a in document("../docs/xmpbib.xml")//author

order by $a/last empty least , $a/first empty least

return $a return $authors/lastResult:<last>Stevens</last>,<last>Stevens</last>,<last>Abiteboul</last>,<last>Buneman</last>,<last>Suciu</last>

Another Ordering Example

for $a in document("../docs/xmpbib.xml")//author order by $a/last empty least , $a/first empty

least return $a/lastResult:<last>Abiteboul</last>,<last>Buneman</last>,<last>Stevens</last>,<last>Stevens</last>,<last>Suciu</last>

Predicates

let $a := (1,2,3) [. > 2 or . = 1]

return

$a

Result:

1, 3

Predicates

let $a := (1,2,3) [. > 2 or . = 1]for $i in $areturn <r>{ $i }</r>Result:<r>1</r>, <r>3</r>

Computing Content

for $t in (document("../docs/xmpbib.xml")//title) [count(../author) < 3 ]

return <review> { $t } </review>

Result:<review><title>TCP/IP Illustrated</title></review>,<review><title>Advanced Programming in the Unix environment</title></review>,<review> <title>The Economics of Technology and Content for Digital TV</title></review>

Returning a Variable Content

let $i := (1, 2, 3)

return

$i

Result:

1, 2, 3

Computing Content

for $b in document("../docs/xmpbib.xml")//book

return <quote> {$b/title , $b/price} </quote>

Result:<quote><title>TCP/IP Illustrated</title><price>65.95</price></quote>,<quote> <title>Advanced Programming in the Unix environment</title> <price>65.95</price></quote>,<quote><title>Data on the Web</title><price>39.95</price></quote>,<quote> <title>The Economics of Technology and Content for Digital TV</title> <price>129.95</price></quote>

Computing Content – Similar


return

<quote>

{$b/author , $b/price}

</quote>

Result: Next slide

Result: Computing Content

<quote>

<author><last>Stevens</last><first>W.</first></author>

<price>65.95</price>

</quote>,

<quote>

<author><last>Stevens</last><first>W.</first></author>


</quote>,

<quote>

<author><last>Abiteboul</last><first>Serge</first></author>

<author><last>Buneman</last><first>Peter</first></author>

<author><last>Suciu</last><first>Dan</first></author>


</quote>,

<quote><price>129.95</price></quote>

More Computing Content

let $i := (1, 2, 3)

return

<result>

{for $a in $i

return <a> { $a } </a> }

</result>

Result:

<result><a>1</a><a>2</a><a>3</a></result>

Some Fine Points• The part of a direct element constructor between

the start tag and the end tag is called the content of the element constructor.

• This content may consist of literal text characters, nested element constructors, and expressions enclosed in curly braces.

• In general, the value of an enclosed expression may be any sequence of nodes and/or atomic values.

• Enclosed expressions can be used in the content of an element constructor to compute both the content and the attributes of the constructed node

Conceptually, the content of an element constructor is processed as follows:

1. The content is evaluated to produce a sequence of nodes called the content sequence, as follows:

1. Predefined entity references and character references are expanded into their referenced strings, as described in 3.1.1 Literals.

2. Each consecutive sequence of literal characters evaluates to a single text node containing the characters. However, if the sequence consists entirely of boundary whitespace as defined in 3.7.1.4 Whitespace in Element Content and the Prolog does not specify xmlspace = preserve, then no text node is generated.

3. Each nested element constructor is evaluated according to the rules in this section, resulting in a new element node.

Cont.

4. Enclosed expressions are evaluated as follows: For each node returned by an enclosed expression, a new deep copy of the node is constructed, including all its children, attributes, and namespace nodes (if any). Each copied node has a new node identity. Copied element nodes are given the type annotation xs:anyType, and copied attribute nodes are given the type annotation xs:anySimpleType. For each adjacent sequence of one or more atomic values returned by an enclosed expression, a new text node is constructed, containing the result of casting each atomic value to a string, with a single blank character inserted between adjacent values.

Cont.

2. If the content sequence contains a document node, a type error is raised.[err:XQ0023]

3. If the content sequence contains an attribute node following a node that is not an attribute node, a type error is raised.[err:XQ0024] Attribute nodes occurring at the beginning of the content sequence become attributes of the new element node. If two or more attributes of the new element node have the same name, a dynamic error is raised.[err:XQ0025]

Cont.

4. Adjacent text nodes in the content sequence are coalesced into a single text node by concatenating their contents, with no intervening blanks.

5. The resulting sequence of nodes becomes the children and attributes of the new element node in the data model representation.

6. The new element node is automatically validated, as described in 3.7.1.5 Type of a Constructed Element.

Examples

• Example: <a>{1}</a> The constructed element node has

one child, a text node containing the value "1".• Example: <a>{1, 2, 3}</a> The constructed element

node has one child, a text node containing the value "1 2 3".

• Example: <c>{1}{2}{3}</c> The constructed element

node has one child, a text node containing the value "123".

Examples

• Example: <b>{1, "2", "3"}</b> The constructed element

node has one child, a text node containing the value "1 2 3".

• Example: <fact>I saw 8 cats.</fact> The constructed

element node has one child, a text node containing the value "I saw 8 cats.".

• Example: <fact>I saw {5 + 3} cats.</fact> The

constructed element node has one child, a text node containing the value "I saw 8 cats.".

Examples

• Example: <fact>I saw <howmany>{5 +

3}</howmany> cats.</fact> The constructed element node has three children: a text node containing "I saw ", a child element node named howmany, and a text node containing " cats.". The child element node in turn has a single text node child containing the value "8".

Example

for $a in document("../docs/xmpbib.xml")//author return <author> {string($a/first) , " ", $a/last} </author>Result:

<author>W. <last>Stevens</last></author>,<author>W. <last>Stevens</last></author>,<author>Serge <last>Abiteboul</last></author>,<author>Peter <last>Buneman</last></author>,<author>Dan <last>Suciu</last></author>

Example for $a in document("../docs/xmpbib.xml")//author return <author> {string($a/first) , " ", string($a/last)} </author> </author>Result:

<author>W. Stevens</author>,<author>W. Stevens</author>,<author>Serge Abiteboul</author>,<author>Peter Buneman</author>,<author>Dan Suciu</author>

Example (XHTML)document { <table border="1"> <thead> <tr> <td>Title</td> <td>Publisher</td> <td>Price</td> <td>Year</td> </tr> </thead> <tbody> <tr> <td>TCP/IP</td> <td>Addison</td> <td>29.95</td> <td>1994</td> </tr> <tr> <td>Elements and

Attributes</td> <td>Weston</td> <td>23</td> <td>2002</td> </tr> </tbody></table>}

Title Publisher Price Year

TCP/IP Addison 29.95 1994

Elements and Attributes

Weston 23 2002

let $t := document("bib.xhtml") return $t

Result

Use “at” - Translate XHTML “Obvious” XML

let $t := document("bib.xhtml")//tablefor $r in $t/tbody/tr return <book> { for $c at $i in $r/td return element { lower-case(data($t/thead/tr/td[$i])) } { string($c) } } </book>Result: Next slide

Result

<book> <title>TCP/IP</title> <publisher>Addison</publisher> <price>29.95</price> <year>1994</year></book>,<book> <title>Elements and Attributes</title> <publisher>Weston</publisher> <price>23</price> <year>2002</year></book>

distinct

distinct-values( document("../docs/xmpbib.xml")//author/last )

Result:


<last>Abiteboul</last>,

<last>Buneman</last>,

<last>Suciu</last>

distinct-values

for $a in distinct-values( document("../docs/xmpbib.xml")//author )

return $a

Result:<author><last>Stevens</last><first>W.</first></author>,

<author><last>Abiteboul</last><first>Serge</first></author>,


<author><last>Suciu</last><first>Dan</first></author>

Distinct

let $a := (<book>Elements Are Redundant</book>, <book>Elements Are Redundant</book>)

return

<a>

{ distinct-nodes($a) }

but

{ distinct-values($a) }

</a>

Result<a><book>Elements Are Redundant</book><book>Elements Are Redundant</book> but<book>Elements Are Redundant</book></a>

Larger font:

<a><book>Elements Are Redundant</book><book>Elements Are Redundant</book>

but<book>Elements Are Redundant</book></a>

distinct-nodes

• fn:distinct-nodes($srcval as node*) as node* • Returns the sequence that results from removing

from $srcval all but one of a set of nodes that have the same identity as one another, based on node identity (that is, using op:node-equal()). The order in which the distinct nodes are returned is ·implementation dependent·. If $srcval is the empty sequence, returns the empty sequence. For detailed semantics see section 6.2.2 of [XQuery 1.0 and XPath 2.0 Formal Semantics].

distinct-values• fn:distinct-

values($srcval as xs:anyAtomicType*) as xs:anyAtomicType* • fn:distinct-values($srcval as xs:anyAtomicType*,

$collationLiteral as xs:string) as xs:anyAtomicType*• Returns the sequence that results from removing from $srcval all

but one of a set of values that are eq to one other. All the values must be of a single type or one of its subtypes (for numeric values, the numeric promotion rules defined in 6.2 Operators on Numeric Values are used to promote all values to a single common type).

• The type returned is a sequence of values of the same type as $srcval. The type must have a total order. If this condition is not satisfied, an error is raised ("Type does not have total order"). Equality must also be defined for the type. If this condition is not satisfied, an error is raised ("Type does not have equality defined"). For detailed semantics see section 6.2.2 of [XQuery 1.0 and XPath 2.0 Formal Semantics].

distinct-values

• If $collationLiteral is not in the lexical space of xs:anyURI an error is raised ("Invalid collationURI").

• If $srcval is the empty sequence, the empty sequence is returned.

• For xs:float and xs:double values, NaN is considered to be equal to itself and 0.0 is equal to -0.0.

• If an xs:dateTime, xs:date or xs:time value does not have a timezone, an implicit timezone is provided by the evaluation context. The normalized value is adjusted using this implicit timezone if necessary. The adjusted normalized value is used to compute distinctness. If multiple adjusted normalized values compare equal but the accompanying timezones are different, it is ·implementation dependent· which value is returned.

distinct-values

• Equality of string values is determined according to the collation that is used. The order of the values returned is ·implementation dependent·. The collation used by the invocation of this function is determined according to the rules in 7.3 Equality and Comparison of Strings. If the type of the items in $srcval is not xs:string and $collationLiteral is specified, the collation is ignored.

• 15.1.11.1 Examples• fn:distinct-values(1, 2.0, 3, 2) returns (1, 3, 2.0).• So, what about semantics for node sequence argument?

List by Authorlet $books := document("../docs/xmpbib.xml")//bibreturn<authlist> {

for $a in distinct-values($books//author) order by $a return <author> <name> { $a/last/text() } </name> <books> {

for $b in $books//book [author = $a] order by $b/title return $b/title } </books> </author> }</authlist>

Could we use distinct-nodes?

Result<authlist> <author> <name>Abiteboul</name> <books><title>Data on the Web</title></books> </author> <author> <name>Buneman</name> <books><title>Data on the Web</title></books> </author> <author> <name>Stevens</name> <books> <title>Advanced Programming in the Unix environment</title> <title>TCP/IP Illustrated</title> </books> </author> <author> <name>Suciu</name> <books><title>Data on the Web</title></books> </author></authlist>

More Examples with Distinctfor $a in distinct-values( document("../docs/xmpbib.xml")//author ) for $l in distinct-values($a/last), $f in distinct-values($a [ last = $l]/first) return <author> <last> { $l } </last> <first> { $f } </first> </author>

Result: Next slide

Result<author> <last><last>Stevens</last></last> <first><first>W.</first></first></author>,<author> <last><last>Abiteboul</last></last> <first><first>Serge</first></first></author>,<author> <last><last>Buneman</last></last> <first><first>Peter</first></first></author>,<author> <last><last>Suciu</last></last> <first><first>Dan</first></first></author>

Concatenate


return

op:concatenate(distinct-values( $a ) , distinct-nodes($a))

Result

<book>Elements Are Redundant</book>,

<book>Elements Are Redundant</book>,

<book>Elements Are Redundant</book>

Concatenate

• op:concatenate($seq1 as item*, $seq2 as item*) as item*

• Returns a sequence consisting of the items in $seq1 followed by the items in $seq2. This function backs up the infix operator ",". If either sequence is the empty sequence, the other operand is returned.

• 15.1.5.1 Examples• op:concatenate((1 2 3), (4 5)) returns (1 2 3 4 5).• op:concatenate((), ()) returns ().

Data


return

data($a)

Result:Elements Are Redundant, Elements Are Redundant

Data

data(

<book> <title>Attributes <bold>are</bold> Redundant</title> <price>12.30</price>

</book>)

Result:

Attributes are Redundant12.30

Data

• fn:data($srcval as item*) as xdt:anyAtomicType* • fn:data takes a sequence of items and returns a

sequence of atomic values.• The result of fn:data is the sequence of atomic

values produced by applying the following rules to each item in $srcval:

• If the item is an atomic value, it is returned.• If the item is a node, fn:data() returns the typed

value of the node as defined by the accessor function dm:typed-value in [XQuery 1.0 and XPath 2.0 Data Model].

dm:typed-value• dm:typed-value($n as Node) as xdt:anyAtomicType* • The dm:typed-value accessor returns the typed-value of the node,

which is a sequence of zero or more atomic values derived from the string-value of the node and its type in such a way as to be consistent with validation.

• If the node is a comment, document, namespace, processing-instruction, or text node, then its typed value is equal to its string value as an instance of xdt:untypedAtomic.

• If the node is an attribute node with type xs:anySimpleType, then its typed value is equal to its string value as an instance of xdt:untypedAtomic. The typed value of an attribute node with any other type is derived from its string value and type annotation in a way that is consistent with XML Schema validation.

• If the node is an element node with type xs:anyType, then its typed value is equal to its string value, as an instance of xdt:untypedAtomic.

dm:typed-value (Cont.)• If the node is an element node with a simple type or with a complex

type of simple content, then its typed value is derived from its string value and type in a way that is consistent with XML Schema validation.

• If the item is an element node with complex type of empty content, then its typed value is the empty sequence.

• If the node is an element node with a complex type of mixed content, then its typed value is its string value as an instance of xdt:untypedAtomic.

• Recall dm:string-value: The concatenation of the string-values of all the text node descendants of the element in document order.

• If the item is an element node with complex type of complex content, then its typed value is undefined and dm:typed-value raises a type error, which may be handled by the host language.

• For detailed semantics see [XQuery 1.0 Formal Semantics].

A note on Understanding the Spec

• The basics are:– The Xpath 2.0 and Xquery 1.0 data model.– XML Schema.– Sequence types (Xquery).

• Next come built-in functions and operators.

• Next come Xquery expressions.

Join – File xmpreviews1.xml

<?xml version="1.0" encoding="ISO-8859-1"?><reviews> <entry> <title>TCP/IP Illustrated</title> <price>65.95</price> <review> One of the best books on TCP/IP. </review> </entry></reviews>

Join

for $t in document("../docs/xmpbib.xml")//title,

$e in document("../docs/xmpreviews.xml")//entry

where $t = $e/title

return

<entry> { $t, $e/review }</entry>

Result: Next slide

Result<entry> <title>TCP/IP Illustrated</title> <review> One of the best books on TCP/IP. </review></entry>,<entry> <title>Advanced Programming in the Unix environment</title> <review> A clear and detailed discussion of UNIX programming. </review></entry>,<entry> <title>Data on the Web</title> <review> A very good discussion of semi-structured database systems and XML. </review></entry>

Join – Another way

for $t in document("../docs/xmpbib.xml")//title return <reviewentry> { $t } {for $e in document("xmpreviews1.xml")//entry where $t = $e/title return $e/review } </reviewentry>Result: Next slide

Result<reviewentry> <title>TCP/IP Illustrated</title> <review> One of the best books on TCP/IP. </review></reviewentry>,<reviewentry> <title>Advanced Programming in the Unix environment</title></reviewentry>,<reviewentry><title>Data on the Web</title></reviewentry>,<reviewentry> <title>The Economics of Technology and Content for Digital TV</title></reviewentry>

Hierarchy Inversion<listings>{ for $p in distinct-values(document("../docs/xmpbib.xml")//publisher) order by $p return <result> { $p } { for $b in document("../docs/xmpbib.xml")/bib/book where $b/publisher = $p order by $b/title return $b/title } </result>}</listings>Result: Next slide

Result<listings> <result> <publisher>Addison-Wesley</publisher> <title>Advanced Programming in the Unix environment</title> <title>TCP/IP Illustrated</title> </result> <result> <publisher>Kluwer Academic Publishers</publisher> <title>The Economics of Technology and Content for Digital

TV</title> </result> <result> <publisher>Morgan Kaufmann Publishers</publisher> <title>Data on the Web</title> </result></listings>

Existential Quantifiers


where some $a in $b//author

satisfies ($a/last="Stevens" and $a/first="W.")

return $b/title

Result:

<title>TCP/IP Illustrated</title>,

<title>Advanced Programming in the Unix environment</title>

Universal Quantifiers

for $b in document("../docs/xmpbib.xml")//book where every $a in $b//author satisfies ($a/last="Stevens" and

$a/first="W.") return $b/titleResult: (note the empty satisfaction in the 3rd title)<title>TCP/IP Illustrated</title>,<title>Advanced Programming in the Unix

environment</title>,<title>The Economics of Technology and

Content for Digital TV</title>

Example: Books per Author<author-list>{let $a := document("../docs/xmpbib.xml")//author for $l in distinct-values($a/last), $f in distinct-values($a [ last = $l]/first) order by data($l), data($f) return <author> <name> { $l , " ", $f } </name> { for $b in document("../docs/xmpbib.xml")//bib/book where some $ba in $b/author satisfies ($ba/last= $l and $ba/first = $f) order by $b/title return $b/title } </author>}</author-list>

Result<author-list> <author> <name><last>Abiteboul</last> <first>Serge</first></name> <title>Data on the Web</title> </author> <author> <name><last>Buneman</last> <first>Peter</first></name> <title>Data on the Web</title> </author> <author> <name><last>Stevens</last> <first>W.</first></name> <title>Advanced Programming in the Unix environment</title> <title>TCP/IP Illustrated</title> </author> <author> <name><last>Suciu</last> <first>Dan</first></name> <title>Data on the Web</title> </author></author-list>

One Morefor $b in document("../docs/xmpbib.xml")//bookreturn <book> { $b/title } { for $a at $i in $b/author where $i <= 2 return <author> { string($a/last), ",", string($a/first) } </author> } { if (count($b/author) > 2) then <author> et. al. </author> else () } </book>

Result

<book><title>TCP/IP Illustrated</title><author>Stevens , W.</author></book>,

<book> <title>Advanced Programming in the Unix environment</title> <author>Stevens , W.</author></book>,<book> <title>Data on the Web</title> <author>Abiteboul , Serge</author> <author>Buneman , Peter</author> <author> et. al. </author></book>,<book> <title>The Economics of Technology and Content for Digital TV</title></book>

mybook.xml <section title="Intro"> <section title="Background"> </section> <section title="Related Work"> </section> </section> <section title="Definitions"> </section> <section title="The System"> <section title="Design"> </section> <section title="Implementation"> <section title="Overview"> </section> <section title="Detailed"> </section> </section> </section>

Recursive Functionsdefine function toc($book-or-section as element) as

element*{ for $s in $book-or-section/section return <section> { $s/@title, toc($s) } </section>}<toc> { for $a in document("mybook.xml")/book return toc($a) }</toc>Result: Next slide

Result<toc> <section title="Intro"> <section title="Background"></section> <section title="Related Work"></section> </section> <section title="Definitions"></section> <section title="The System"> <section title="Design"></section> <section title="Implementation"> <section title="Overview"></section> <section title="Detailed"></section> </section> </section></toc>

Tracedefine function toc($book-or-section as element) as element*{ for $s in $book-or-section/section return <section> { $s/@title, toc( trace($s, " ARG1 ") ) } </section>}<toc> { for $a in document("mybook.xml")/book return toc( trace($a, " ARG ") ) }</toc>

Result: Next slide

ARG <book> <section title="Intro"> <section title="Background"> Some background ... </section> <section title="Related Work"> Some papers ... </section> </section> <section title="Definitions"> some defs ... </section> <section title="The System"> <section title="Design"> System design ... </section> <section title="Implementation"> <section title="Overview"> Overview ... </section> <section title="Detailed"> The details ... </section> </section> </section></book> ARG1 <section title="Intro"> <section title="Background"> Some background ... </section> <section title="Related Work"> Some papers ... </section> </section> ARG1 <section title="Background"> Some background ... </section> ARG1 <section title="Related Work"> Some papers ... </section> ARG1 <section title="Definitions"> some defs ... </section> ARG1 <section title="The System"> <section title="Design"> System design ... </section> <section title="Implementation"> <section title="Overview"> Overview ... </section> <section title="Detailed"> The details ... </section> </section>

</section> ARG1 <section title="Design"> System design ... </section> ARG1 <section

title="Implementation"> <section title="Overview"> Overview ... </section> <section title="Detailed"> The details ... </section> </section> ARG1 <section title="Overview"> Overview ... </section> ARG1 <section title="Detailed"> The details ... </section><toc> <section title="Intro"> <section title="Background"></section> <section title="Related Work"></section> </section> <section title="Definitions"></section> <section title="The System"> <section title="Design"></section> <section title="Implementation"> <section title="Overview"></section> <section title="Detailed"></section> </section> </section></toc>

Assignment• Modify the previous program so that the output in general is of the form such that

under each section each first-level child section is indented by 5 spaces,

• For example: <toc> Intro Background Related Work Definitions The System Design Implementation Overview Detailed </toc>:

xquery introduction by examples. sources xquery 1.0: an xml query languagew3c working draft 22...

Documents

slide slide

web slide

result expression

btitle result

cowen smith slide

purple crayon slide

cowen smith result

document creation expression