Pal gov.tutorial3.session3.xpath & xquery (lab1)

‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps

Tutorial III:
Process Integration and Service Oriented Architectures

Session 3
Xpath & Xquery
Prepared By

Ismail Romi
Palestine Polytechnic University (PPU)
Email: ismailr@ppu.edu

Reviewed by
Prof. Marco Ronchetti and Prof. Paolo 2011
PalGov © Bouquet, Trento University, Italy 1

About

This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the
Commission of the European Communities, grant agreement 511159-TEMPUS-1-
2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )

Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium

Palestine Technical University, Palestine
Université de Savoie, France

Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine

Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

© Copyright Notes
Everyone is encouraged to use this material, or part of it, but should
properly cite the project (logo and website), and the author of that part.

No part of this tutorial may be reproduced or modified in any form or by
any means, without prior written permission from the project, who have
the full copyrights on the material.

Attribution-NonCommercial-ShareAlike
CC-BY-NC-SA

This license lets others remix, tweak, and build upon your work non-
commercially, as long as they credit you and license their new creations
under the identical terms.

PalGov © 2011 3

Tutorial Map

Intended Learning Objectives
A: Knowledge and Understanding
Title T Name
3a1: Demonstrate knowledge of the fundamentals of middleware.
3a2: Describe the concept behind web service protocols.
Session0: Syllabus and overview 0 Aldasht
3a3: Explain the concept of service oriented architecture. Sesson1: Introduction to SOA 2 Aldasht
3a4: Explain the concept of enterprise service bus. Session2: XML namespaces & XML schema 2 Aldasht
3a5: Understanding WSDL service interfaces in UDDI. Session 3: Xpath & Xquery 4 Romi
B: Intellectual Skills Session4: REST web services 3 M. Melhem
3b1: Design, develop, and deploy applications based on Service Session5: Lab2: Practice on REST 3 M. Melhem
Oriented Architecture (SOA). Session 6: SOAP 2 Aldasht
3b2: use Business Process Execution Language (BPEL). Session 7: WSDL 3 Aldasht
3b3: using WSDL to describe web services.
Session8: Lab 3: WSDL practice 3 Aldasht
C: Professional and Practical Skills Session9: ESB 4 Aldasht
3c1: setup, Invoke, and deploy web services using integrated
Session10: Lab4: Practice on ESB 4 Aldasht
development environment.
Session11: integration patterns 4 M. Melhem
3c2: construct and use REST and SOAP messages for web
services communication. Session12: Lab5: integration patterns 4 M. Melhem
D: General and Transferable Skills Session13: BPEL 3 Aldasht
d1: Working with team. Session14: Lab6: Practice on BPEL 3 Aldasht
d2: Presenting and defending ideas. Session15: UDDI 2 Aldasht
d3: Use of creativity and innovation in problem solving.
d4: Develop communication skills and logical reasoning abilities.

PalGov © 2011 4

XPath: Content

• Ways of looking at an XML document.
• How to visualize XPath and how the component parts of XPath
syntax fit together to enable you to navigate around the XPath
data model.
• The XPath axes—the “directions” that are available to navigate
around the XPath data model
• XPath 1.0 functions

PalGov © 2011 5

Ways of Looking at an XML Document

• The W3C has developed three specifications:
– XPath
– XML Document Object Model (DOM)
– XML Information Set
• each of which represents a logical model of an XML
document in similar but distinct ways.

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Modeling XML Documents

1. The XPath data model:
– Represents most parts of a serialized XML document as a tree
of nodes.
2. The Document Object Model:
– Represents an XML document as a hierarchical tree of nodes.
3. The XMLInformation Set:
– Represents an XMLdocument as a hierarchical tree but uses a
different approach from both the XPath model and the DOM.
– The XMLInformation Set recommendation is located at
http://www.w3.org/TR/xml-infoset/.

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Visualizing XPath

 XPath can be considered as a street directions around the
hierarchical tree of nodes that make up the XPath data
model (Axes).
 XPath expressions starts from a standard point, (the root
node).
 In XPath, the starting point is called the context.
 All legal XPath code can be called an expression.
 An XPath expression that returns a node-set is called a
location path.

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Visualizing Xpath …Cont

• There are 13 directions that can be used.
• In XPath, a direction is called an axis.
• Example:
– /Book/Chapter[@number=2]

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Understanding Context

• The context indicates the location of the node where a
processor is currently situated.
• That node is called the context node.

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What Is a Node?

• A node is a representation in the XPath data model of a
logical part of an XML document.
• Types:
 Root node
 Element node
 Attribut node
 Text node
 Namespace node
 Comment node
 Processing Instruction node

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Root Node

• The root node represents the document itself, independent
of any content.
• The root node is the apex of the hierarchy of nodes that
represents an XML document.
• It has no name and cannot be seen when the document is
serialized.
• The root node just serves as a starting point when
navigating the document.
• The root element, is the first element in the document and
is a child of the root node.

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Element Node

• Each element in an XML document is represented as an
element node in the XPath data model.
• Element nodes have a name that consists of the
namespace URI of the element and the local part of its
name.
The following is an XML document:
<?xml version="1.0" encoding="ISO-8859-
1"?>

<bookstore>
<book> Root Element Node
<title lang="en"> Learning XML </title>
<author> Ray </author>
<year>2003</year>
</book>
</bookstore> Element Node

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Attribute Node

• Each attribute in an XML document is represented in the
XPath model as an attribute node.
• The element node with which the attribute node is
associated is said to be the parent node of the attribute
node.
• Attribute nodes have a name and a value.
Example:
1"?>
<bookstore>
<book>
<year>2003</year>
</book> Attribute Node
</bookstore>

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Text Node

• Text content of an element node is represented in the
XPath data model as a text node.
• The string value of a text node is its character data.
• A text node does not have a name.
Example:
1"?>
Text Node
<bookstore>
<book>
<year>2003</year>
</book>
</bookstore>

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Namespace Node

• Although a specific node can only belong to one
namespace.
• Any number of in-scope namespaces can be in effect for
the node.
• In-scope namespaces are those for which there exists a
valid prefix to URI mapping or where a URI is associated
with an empty prefix, the default namespace.
The following is an XML document:
1"?>
Namespace Node
<bookstore>
<book>
<ppu:author> Ray </author>
<year>2003</year>
</book>
</bookstore>
PalGov © 2011 16

Comment Node

• A comment node represents a comment in the XML
document.
• Comments in the document type declaration are not
represented in the XPath data model.

Example:
1"?>
Comment Node
<bookstore>

<book>
<year>2003</year>
</book>
</bookstore>

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Processing Instruction Node (PI)

• A processing instruction node in the XPath model
represents a processing instruction in the corresponding
XML document.
• The name of a processing instruction node is its target.
• The string value of a processing instruction node is its
content, excluding the target.
• Example Of PI’s:
•For MS Word 2003 the PI situated right after the XML
declaration looks like this:
<?mso-application progid="Word.Document"?>
•For MS Excel 2003 the PI looks like this:
<?mso-application progid="Excel.Sheet"?>

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Location Paths

• An expression that specifies how to navigate an XPath tree
from one node to another.
• A location path is composed of location steps, each of
which is composed of:
– An “axis,”
– A “node test”
– An optional “predicate.”
• To locate a specific node in an XML document, we put
together multiple location steps, each of which refines the
search.

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XPath 1.0 Axes
Axis Name Ordering Description

self none The context node itself.
parent reverse The context node’s parent, if one exists.
child forward The context node’s children, if they exist.
ancestor reverse The context node’s ancestors, if they exist.
ancestor-or-self reverse The context node’s ancestors and also itself.
descendant forward The context node’s descendants.
descendant-or-self forward The context node’s descendants and also itself.

following forward The nodes in the XML document following the
context node, not including descendants.
following-sibling forward The sibling nodes following the context node.
preceding reverse The nodes in the XML document preceding the
context node, not including ancestors.
preceding-sibling reverse The sibling nodes preceding the context node.

attribute forward The attribute nodes of the context node.
namespace forward The namespace nodes of the context node.

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Parent Axis

• Each element and attribute has one parent.
• Example
<book>
<title>Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
– book element is the parent of the title, author, year, and price:

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Child Axis

• Element nodes may have zero, one or more children.
• Example
<book>
<year>2005</year>
</book>
– title, author, year, and price elements are all children of the book
element:

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Siblings

• Nodes that have the same parent.
• Example:
<book>
<year>2005</year>
</book>
– title, author, year, and price elements are all siblings.

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Ancestors

• Node's parent, parent's parent, etc.
• Example:
<bookstore>
<book>
<year>2005</year>
</book>
</bookstore>
– The ancestors of the title element are the book element and the
bookstore element.

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Descendants

• A node's children, children's children, etc.
• Example:
<bookstore>
<book>
<year>2005</year>
</book>
</bookstore>
– Descendants of the bookstore element are the book, title, author,
year, and price elements.

PalGov © 2011 25

Location Path Expression

• An XPath expression returns either a node-set, a string,
a Boolean, or a number.
• A location path can be absolute or relative.
– An absolute location path starts with a slash ( / )
– A relative location path does not.
• In both cases the location path consists of one or more
steps.
• Examples:
• An absolute location path:
/step/step/...
• A relative location path:
step/step/...

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Location Path Expression…Cont

• The syntax for a location step is:

axisname::nodetest[predicate]

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• Example:
<?xml version="1.0" encoding="ISO-8859-1"?>
…………
…………
<bookstore>
<book>
<title lang="en">Harry Potter</title>
<year>2005</year>
</book>
</bookstore>

PalGov © 2011 28

axisname::nodetest[predicate]
Example Result
child::book Selects all book nodes that are children of the
current node
attribute::lang Selects the lang attribute of the current node
child::* Selects all children of the current node
attribute::* Selects all attributes of the current node
child::text() Selects all text child nodes of the current node
child::node() Selects all child nodes of the current node
descendant::book Selects all book descendants of the current
node
ancestor::book Selects all book ancestors of the current node
ancestor-or- Selects all book ancestors of the current node
self::book - and the current as well if it is a book node
child::*/child::price Selects all price grandchildren of the current
node

PalGov © 2011 29

Node Test Description

* Selects all nodes of
the same principal node
type.
node() Selects all nodes,
regardless of their
type.
text() Selects all text nodes.
comment() Selects all comment
nodes.
processing- Selects all processing-
instruction() instruction nodes.
node name Selects all nodes with
the specified node
name.

Steps Operators:
slash (/)Separates location steps.
double-slash (//)Abbreviation for the location path
PalGov © 2011 30

Xpath Operators
Operator Description Example Return value
| Performs the union of two node- //book | //cd Returns a node-set with all
sets book and cd elements
+ Addition 6+4 10
- Subtraction 6-4 2
* Multiplication 6*4 24
div Division 8 div 4 2
= Equal price=9.80 true if price is 9.80

!= Not equal price!=9.80 false if price is 9.80

< Less than price<9.80 true if price is 9.00
<= Less than or equal to price<=9.80 true if price is 9.00
> Greater than price>9.80 true if price is 9.90

>= Greater than or equal to price>=9.80 true if price is 9.90
or or price=9.80 or price=9.70 true if price is 9.80
and and price>9.00 and price<9.90 true if price is 9.80

mod Modulus (division remainder) 5 mod 2 1

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node-set functions…Examples

Node-set Functions Description

last() Returns the last node in the node-set.

position() Returns the position number of the current
node in the node-set being tested.
count( node-set ) Returns the number of nodes in node-set.
id( string ) Returns the element node whose ID attribute
matches the value specified by argument
string.
local-name( node-set ) Returns the local part of the expanded-name
for the first node in node-set.
namespace-uri( node-set ) Returns the namespace URI of the expanded-
name for the first node in node-set.
name( node-set ) Returns the qualified name for the first
node in node-set.

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Examples

• head/title[ last() ]
– select the last title element node contained in the head element
node
• book[ position() = 3 ]
– select the third book element of the context node. The location
path
– ……
– …..

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Databases: Xquery (the XML Query Language)

• Why XQuery was created.
• How to get started with Xquery.
• How to query an XMLdocument using Xquery.
• XQuery data model.
• XQuery functions.

PalGov © 2011 34

XQuery

• XQuery is to XML what SQL is to database tables.
• XQuery is designed to query XML data - not just XML
files, but anything that can appear as XML, including
databases.
• Xquery is designed around a data model that has the
property to be serialized as XML.
• XML data requires many of the features already
available in DBMS (indexing, security….).
• XQuery is compatible with several W3C standards,
such as XML, Namespaces, XSLT, XPath, and XML
Schema.
• XQuery 1.0 became a W3C Recommendation January
23, 2007.
PalGov © 2011 35

XQuery Tools

• XQuery is still relatively new.
• A large number of software companies and
independent developers have developed partial or
more complete implementations of XQuery.
• W3C updates a web page where links to XQuery
implementations and other sources of useful
XQuery information are included
(www.w3.org/XML/Query).

PalGov © 2011 36

XQuery Tools…Cont

Example:
• Saxon Xquery engine.
• X-Hive Database
• Tamino Database
• Microsoft SQL Server 2005
• Oracle
• Stylus Stodio

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XQuery - Examples of Use

• XQuery can be used to:
– Extract information to use in a Web Service
– Generate summary reports
– Transform XML data to XHTML
– Search Web documents for relevant information

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Extracting Data From XML Document
• Open the xml document:
– The doc() function is used to open the xml
document.
• Path Expressions:
– XQuery uses path expressions to navigate through
elements in an XML document.
• Predicates:
– XQuery uses predicates to limit the extracted data
from XML documents.
• Functions:
– XQuery uses functions to extract data from XML
documents.
PalGov © 2011 39

doc() Function

• Used to open the XML document.
• Exampl books.xml
• Retrieving the previous document:
– doc(books.xml)
• Retrieving part of the document:
– You have to use the Xpath expressions.
– doc("books.xml")/bookstore/book/title

PalGov © 2011 40

Predicates

• XQuery uses predicates to limit the extracted data from
XML documents.
• Example:
– doc("books.xml")/bookstore/book[price<30]

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XQuery Basic Syntax Rules

• XQuery is case-sensitive
• XQuery elements, attributes, and variables must
be valid XML names
• An XQuery string value can be in single or double
quotes
• An XQuery variable is defined with a $ followed by
a name, e.g. $bookstore
• XQuery comments are delimited by (: and :)
• Example:
(: XQuery Comment :)

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XQuery FLWOR Expressions
(for, let, where, order by, return)
• for clause selects all elements.
• where clause selects only elements with a specified
predicate.
• order by clause defines the sort-order.
• return clause specifies what should be returned.
• let clause allows variable assignments.

PalGov © 2011 43

for , return expressions

• Used for looping
• Example:
for $x in doc("books.xml")/bookstore/book
return $x/title
• This for:
– loops all bookstore/book
– returns the title element
• $x: variable name

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Filtering with where clause

• where used in for expression to filter the returned values.
• Example:
where $x/price>30
return $x/title

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Sorting using order by clause

• Used to sort the output in a specified order.
• Example:
where $x/price>30
order by $x/title
return $x/title

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The let Clause

• The let clause:
– allows variable assignments
– avoids repeating the same expression many times.
– does not result in iteration.
• Example:
let $x := "Ahmad"
return <name>{$x}</name>
Output:
<name> Ahmad </name>

PalGov © 2011 47

If-Then-Else
• An XQuery Conditional Expressions.
• Example:
return if ($x/@category="CHILDREN")
then <child>{data($x/title)}</child>
else <adult>{data($x/title)}</adult>
• Notes:
– $x: refers to variable name x
– @ refers to an attribute
– parentheses around the if expression are required.
– else is required, but it can be just else ().

PalGov © 2011 48

XQuery Adding Elements and Attributes

• You can add elements and attributes to the output
document.
Example:
for $x in doc("books.xml")/bookstore/book/title
return $x, <name> ali </name>
• This example adds name element to the output stream.

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Xquery Functions

• XQuery includes over 100 built-in functions.
• There are functions for string values, numeric
values, date and time comparison, node and
QName manipulation, sequence manipulation,
Boolean values, and more.
• Functions found in the w3c web site:
www.w3.org/tr/xpath-functions

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Examples of built-in Function

<name>{uppercase($booktitle)}</name>

order by $x/title
return $x/data(title)

Note: you have to practice w3c Xquery functions.

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Xquery and HTML

• You can generate an HTML document using Xquery.
• You can add elements
• You can add attribute.

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Example1:

Xquery expression:
<ul>
{
order by $x
return <li>{$x}</li>
}
</ul>
Output:
<ul>
<li><title lang="en">Everyday Italian</title></li>
<li><title lang="en">Harry Potter</title></li>
<li><title lang="en">Learning XML</title></li>
<li><title lang="en">XQuery Kick Start</title></li>
</ul>

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Example2
• Xquery expression:
<ul>
{
order by $x
return <li>{data($x)}</li>
}
</ul>
• Out put / HTML
<ul>
<li>Everyday Italian</li>
<li>Harry Potter</li>
<li>Learning XML</li>
<li>XQuery Kick Start</li>
</ul>

PalGov © 2011 54

Example 3

• Xquery:
<html>
<body>

<h1>Bookstore</h1>

<ul>
{
order by $x/title
return <li>{data($x/title)}. Category: {data($x/@category)}</li>
}
</ul>

</body>
</html>
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Example 3….Cont

• Out put:
<html>
<body>

<h1>Bookstore</h1>

<ul>
<li>Everyday Italian. Category: COOKING</li>
<li>Harry Potter. Category: CHILDREN</li>
<li>Learning XML. Category: WEB</li>
<li>XQuery Kick Start. Category: WEB</li>
</ul>

</body>
</html>

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References

1. Hunter, H, Rafter, J., Fawcett, J., Vlist, E., Ayers, D., Duckett, J., Watt, A.,
McKinnon,L., (2007), "Beginning XML", 4th Ed.,Wiley Publishing Inc: Indiana, USA.
2. Ray, E., (2003), "Learning XML", 2nd Ed., O’Rreilly Media Inc.: USA.
3. http://www.w3.org
4. http://www.w3schools.com
5. http://www.xml.com
6. http://www.xml.org

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Pal gov.tutorial3.session3.xpath & xquery (lab1)

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