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MANAGING INFORMATION (CSCU9T4)

LECTURE 5: XML STYLE

Gabriela Ochoa

http://www.cs.stir.ac.uk/~goc/

CONTENT

Revise XML Schema example

Content vs. Display (e.g. Word vs. XML)

XSL: eXtensible Stylesheet Language. A style

sheet language for XML documents.

XSLT: XSL Transformations. A language for

transforming XML documents

XPath: a language for navigating in XML

documents

A number of examples

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http://www.cs.stir.ac.uk/~goc/

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RESOURCES

Books

XML in a Nutshell (2004) by Elliotte

Rusty Harold, W. Scott Means, O'Reilly

XML 1.1 Bible (2004) by Elliotte Rusty

Harold, Wiley

Internet & World Wide Web How to

Program, 5/e by Paul J. Deitel, Harvey M.

Deitel, Abbey Deitel

Links and websites W3 ORG

XML Tutorial: W3Schools

XML.COM O’REALLY

XSLT Online Transformations

W3 Schools: XLST online Editor

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WHAT IS XSL?

XSL stands for eXtensible Stylesheet Language,

and is a style sheet language for XML documents

An XSL style sheet is, like with CSS, a file that

describes how to display an XML document of a

given type

XSL consists of 2 components:

XSLT - a language for transforming XML documents

XSL-FO - a language for formatting XML documents

Related tools

XPath - a language for navigating in XML documents.

XSLT uses XPath to find information in an XML doc

XQuery - a language for querying XML documents

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http://www.w3.org/Style/XSL/WhatIsXSL.htmlhttp://www.w3.org/Style/XSL/WhatIsXSL.htmlhttp://www.w3.org/Style/XSL/WhatIsXSL.htmlhttp://www.xml.com/pub/a/98/10/guide0.htmlhttp://www.utilities-online.info/xsltransformation/.VQPxPxCsUqshttp://www.w3schools.com/xsl/default.asp

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HOW DOES XLST WORK?

Styling requires:

1. A source XML document, containing the information that

the style sheet will display

2. The style sheet itself which describes how to display a

document of a given type. 5

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XSLT STYLESHEETS

Declarative language

Use pattern matching and templates to specify the

transformation

Vastly more expressive than a CSS stylesheets

May perform arbitrary computations

XSLT transformation can be done either on the

client (e.g. Explorer or Mozilla), or on the server

(e.g. Apache Xalan)

The target form is usually another XML document,

commonly XHTML or HTML

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XSLT: AN EXAMPLE TRANSFORMATION

1. Demo: Simple ‘Users’ example in the browser with and w/o stylesheet

2. Example at: http://www.w3schools.com/xml/cd_catalog.xml

Empire Burlesque Bob Dylan USA Columbia 10.90 1985 …

XML file

• No information

about display

• Display is included

in the stylesheet

• Use XSLT to transform XML into HTML, before it is displayed in a browser

• The browser process the transformation

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THE CD CATALOG EXAMPLE

My CD Collection Title Artist

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XSLT PROCESSING MODEL

An XSLT stylesheet consists of a number of template

rules: template rule = pattern + template

For a given input XML document, the output is

obtained as follows:

The source tree is processed by processing the root node

A single node is processed by:

1. finding the template rule with the best matching pattern

2. instantiating its template (creates result fragment + continues

processing recursively)

A node list is processed by processing each node in order

and concatenating the results

Simple illustrative animation: http://cs.au.dk/~amoeller/XML/transformation/p2.html

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STRUCTURE OF A STYLESHEET

An XSLT stylesheet is itself an XML document

… a template rule template …

• Namespace http://www.w3.org/1999/XSL/Transform is used to recognize the XSLT elements.

• The XML document may refer to a stylesheet using the processing

instruction:

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http://cs.au.dk/~amoeller/XML/transformation/p2.htmlhttp://cs.au.dk/~amoeller/XML/transformation/p2.htmlhttp://cs.au.dk/~amoeller/XML/transformation/p2.html

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XLST USES XPATH

XPath is an expression language for addressing parts of an

XML document

Xpath data model provides a tree representation of XML

documents as well as atomic values such as integers, strings,

and Booleans.

It uses path expressions to select a set of nodes or atomic

values in an XML document

Path expressions look very much like the expressions you see

when you work with a traditional computer file system

XPath contains a library of standard functions

XPath is a W3C recommendation

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XPATH DATA MODEL

XPath sees an XML document as a tree structure

The topmost element of the tree is called the root

element.

Each information (XML elements, attributes,

text, etc.) is called a node.

Nodes that XPath can see

Root node

Elements and attributes

Special nodes like comments, processing instructions,

namespace declarations.

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XLST, XML AND TREES The transformation process: XSLT transforms an XML source-tree

into an XML result-tree.

XML Data Representation

sample1.o sample1.cpp sample1.h g++ -c sample1.cpp

XML Tree representation

dependency

object depends

sample1.o sample1.cpp

depends

sample1.h

rule

g++ -c … 13

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subtree

TREE TERMINOLOGY

Root: node without parent (A)

Siblings: nodes share the same parent

Internal node: node with at least one child (A, B, C, F)

External node (leaf ): node without children (E, I, J, K, G, H, D)

Ancestors of a node: parent, grandparent, grand-grandparent, etc.

Descendant of a node: child, grandchild, grand-grandchild, etc.

Depth of a node: number of ancestors

Height of a tree: maximum depth of any node (3)

Degree of a node: the number of its children

Degree of a tree: the maximum number of its node.

Subtree: tree consisting of a node and its descendants

A

B D C

G H E F

I J K

A Tree is an abstract model of a hierarchical structure.

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XPATH SYNTAX

Let us consider the following XML document

Harry Potter 29.99 Learning XML 39.95

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XPATH: SELECTING NODES

XPath uses path expressions to select nodes in an XML document

The most useful path expressions are listed below:

Expression Description

Nodename Selects all nodes with the name "nodename"

/ Selects from the root node

// Selects nodes in the document from the current node

that match the selection no matter where they are

. Selects the current node

.. Selects the parent of the current node,

@ Selects attributes

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XPATH: EXAMPLES OF PATH EXPRESSIONS

Path Expression Selects

bookstore All nodes with the name "bookstore"

/bookstore The root element bookstore

bookstore/book All book elements that are children of bookstore

//book Selects all book elements no matter where they are in the document

bookstore//book

All book elements that are descendant of the

bookstore element, no matter where they are

under the bookstore element

//@lang All attributes that are named lang

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PREDICATES

Are used to find a specific node or a node that contains a specific value.

Are always embedded in square brackets.

Path Expression Selects

/bookstore/book[1] The first book element that is the child of the bookstore element.

/bookstore/book[last()] The last book element that is the child of the bookstore element

/bookstore/book[position()35.00] All the book elements of the bookstore element that have a price element with a value greater

than 35.00

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SELECTING UNKNOWN NODES

Wildcard Description

* Matches any element node

@* Matches any attribute node

node() Matches any node of any kind

XPath wildcards can be used to select unknown XML elements.

Some Examples:

Path Expression Selects

/bookstore/* All the child element nodes of the bookstore element

//* All elements in the document

//title[@*] All title elements which have at least one attribute of any kind

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XPATH: SELECTING SEVERAL PATHS

• By using the | operator in an XPath expression you can select

several paths.

• Some Examples:

Path Expression Select

//book/title | //book/price All the title AND price elements of all book elements

//title | //price All the title AND price elements in the document

/bookstore/book/title | //price All the title elements of the book element of the bookstore element AND all the price

elements in the document

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XPATH AXES

An axis defines a node-set relative to the current node.

Harry Potter 29.99 Learning XML 39.95

Axis Names: • ancestor • ancestor-or-self • attribute • child • descendant • descendant-or-self • following • following-sibling • namespace • parent • preceding • preceding-sibling • self

Example XML:

Details at: http://www.w3schools.com/xpath/xpath_axes.asp

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XPATH: LOCATION PATH EXPRESSION

A location path can be absolute or relative

Absolute locations start with a slash ‘/’: /step/step/...

Relative locations does *not* start with a ‘/’: step/step/...

Location paths consist of one or more steps, each separated

by a slash

Each step is evaluated against the nodes in the current

node-set. A step consists of:

an axis: defines the tree-relationship between the selected

nodes and the current node

a node-test: identifies a node within an axis

zero or more predicates: to further refine the selected node-set

Syntax or a location step:

axisname::nodetest[predicate]

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http://www.w3schools.com/xpath/xpath_axes.asphttp://www.w3schools.com/xpath/xpath_axes.asp

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EXAMPLES: LOCATION PATH EXPRESSION

Example Selects

child::book All book nodes that are children of the current node

attribute::lang The ‘lang’ attribute of the current node

child::* All element children of the current node

attribute::* All attributes of the current node

child::text() All text in the children of the current node

child::node() All children of the current node

descendant::book All book descendants of the current node

ancestor::book All book ancestors of the current node

ancestor-or-self::book All book ancestors of the current node - and the current as well if it is a book node

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BACK TO XSLT • We took some time to cover Xpath

• We get back to explaining more details of XSLT

• Let us first consider the CD Catalog Example

• Then some extensions to it

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HOW DOES XLST WORK?

Styling requires:

1. A source XML document, containing the information that

the style sheet will display

2. The style sheet itself which describes how to display a

document of a given type. 25

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XSLT ELEMENTS

XSLT is based on the idea of templates.

The idea is to specify a number of templates that each

match XML in the source document

When the matching XML is found, the template is

activated and its contents are added to the output

document.

Example:

A template that matches a element.

For each encountered in the source document the corresponding template will be activated

Any code inside the template will be executed and added to

the output

Using templates to process various parts of the source

document, is one of the most powerful features of XSLT 26

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MAIN XSLT ELEMENTS

All-encompassing document element used to hold all

your templates

Use for setting which version of XSLT you want to use

The most important of XLST elements. It has two

features:

1. What items from the source document it should handle

2. What should be added to the output when it is executed

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MAIN XSLT ELEMENTS

:

An alternative way of processing a number of items in a similar fashion (it can also be done with )

Group the items and produce output based on each one

:

Used to evaluate an expression and add the result to the output.

Example:

Process a element

Use to add the contents of its element to the output

:

Responsible for deciding which items in the source document

should be processed

They are then handled by the appropriate template.

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THE CD CATALOG EXAMPLE

My CD Collection Title Artist

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XSLT ELEMENT

A template contains rules to apply when a specified node is

matched.

The element is used to build templates.

The match attribute is used to associate a template with an

XML element or for the entire XML document.

The value of the match attribute is an XPath expression

In the Example:

The match="/" attribute associates the template with the root of

the XML source document.

The content inside the element defines some HTML to write to the output.

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XLST AND

ELEMENT S

Locates elements in the XML document and repeats a

template for each one.

The select attribute describes the element in the source

document.

Selects a child in the hierarchy and

Inserts the content of that child into the template.

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XSLT SORT

The element is used to sort the output

Add an element inside the element in the XSL file:

Demo, by editing the XSL file

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XSLT FILTER

It is possible to have filters to the XML file

Add the filter in a element:

Legal operators are:

= (equal)

=! (not equal)

< (less than)

> (greater than)

Demo, by editing the XSL file

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XSLT CONDITIONAL IF

It is possible to have a conditional if test against the content of the file, by adding an element to your XSL document :

...some output if the expression is true...

Demo, by editing the XSL file (inside the element ):

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THE ELEMENT

Applies a template to the current element or to the

current element's child nodes

If we add a select attribute to the

element it will process only the child element that matches the value of the

attribute.

We can use the select attribute to specify the order

in which the child nodes are processed.

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My CD Collection

… Continue next slide

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Title:
Artist:

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SUMMARY

XSL: eXtensible Stylesheet Language. A style

sheet language for XML documents.

XSLT: XSL Transformations. A language for

transforming XML documents

XPath: a language for navigating in XML

documents

A number of examples with explanations

More XSLT elements listed at : http://www.w3schools.com/xsl/xsl_w3celementref.asp

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http://www.w3schools.com/xsl/xsl_w3celementref.asphttp://www.w3schools.com/xsl/xsl_w3celementref.asp