03 x files

IT6801
SERVICE ORIENTED
ARCHITECTURE
-

UNIT I INTRODUCTION TO XML
XML document structure – Well formed and valid
documents – Namespaces – DTD – XML Schema
– X-Files.

XML and XSLT
With XSLT
One can transform
an XML document into HTML.

Displaying XML with XSLT
• XSLT means eXtensible Stylesheet Language Transformations
• XSLT is the recommended style sheet language for XML.
• XSLT is far more sophisticated than CSS.
• With XSLT, one can
– Add/remove elements and attributes to or from the output file.
– Rearrange and sort elements,
– Perform tests and make decisions about which elements to hide and
display, and a lot more.

XSLT Example
• XSLT uses XPath to find information in an XML document.
<?xml version="1.0" encoding="UTF-8"?>
<breakfast_menu>
  <food>
<name>Belgian Waffles</name>
<price>$5.95</price>
<description>Two of our famous Belgian Waffles with plenty
of real maple syrup</description>
<calories>650</calories>
  </food>
  <food>
<name>Strawberry Belgian Waffles</name>
<description>Light Belgian waffles covered with
              strawberries and whipped cream</description>
  </food>

<food>
<name>Berry-Berry Belgian Waffles</name>
<desription> Light Belgian waffles covered with an
assortment of fresh berries and whipped cream
</description>
  </food>
  <food>
<name>French Toast</name>
<description>Thick slices made from bread</description>
  </food>
  <food>
<name>Homestyle Breakfast</name>
<description> Two eggs, bacon or sausage, toast, and
our ever-popular hash browns </description>
  </food>
</breakfast_menu>

XSLT Example
<html xsl:version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<body style="font-family:Arial;font-size:12pt;
              background-color:#EEEEEE">
<xsl:for-each select="breakfast_menu/food">
  <div style="background-color:teal;color:white;padding:4px">
    <span style="font-weight:bold"><xsl:value-of select="name"/> -
</span>
    <xsl:value-of select="price"/>
  </div>

XSLT Example

<div style="margin-left:20px;margin-bottom:1em;font-size:10pt">
    <p>
    <xsl:value-of select="description"/>
    <span style="font-style:italic">
      (<xsl:value-of select="calories"/> calories per serving)
    </span>
    </p>
  </div>
</xsl:for-each>
</body>
</html>

Displaying XML with XSLT
• This is displayed in a browser:

Xpath
(XML Path language)
A language with a standard syntax
for finding information in an XML document

Introduction
• What is XPath?
– XPath is a syntax for defining parts of an XML document
– XPath uses path expressions to navigate in XML documents
– XPath contains a library of standard functions
– XPath is a major element in XSLT
– XPath is also used in XQuery, XPointer and XLink
– XPath is a W3C recommendation
• XPath was created
– To reduce the amount of time to find the elements and attributes
desired by an author

XPath Path Expressions
• XPath uses path expressions
– To select nodes or node-sets in an XML document.
• XPath expressions can be used in
– JavaScript,
– Java,
– XML Schema,
– PHP,
– Python,
– C and C++, and lots of other languages.

XPath Standard Functions
• XPath 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.

XPath is Used in XSLT
• XPath was designed to be used by
– XSLT,
– XPointer and
– Other XML parsing software.
• Without XPath knowledge
– You will not be able to create XSLT documents.

XPath Terminology - Nodes
• XML documents are treated as trees of nodes.
• Topmost element of the tree is called the root element.
• In XPath, there are seven kinds of nodes:
– Element, attribute, text, namespace, processing-instruction, comment,
and document nodes.

<bookstore>
  <book>
    <title lang="en">Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>
    <price>29.99</price>
  </book>
</bookstore>
Example of nodes in this XML document:
<bookstore> (root element node)
<author>J K. Rowling</author> (element node)
lang="en" (attribute node)
Atomic values are nodes with no children or parent.
Example of atomic values:
J K. Rowling
"en"
Items are atomic values or nodes.

Relationship of Nodes
• Parent - Each element and attribute has one parent.
• Children - Element nodes may have zero, one or more children.
• Siblings - Nodes that have the same parent.
• Ancestors - A node's parent, parent's parent, etc.
• Descendants - A node's children, children's children, etc.
• In this example;
– book element is the parent of the title, author, year, and price
– title, author, year, and price elements are all children of  book element
– title, author, year, and price elements are all siblings
– ancestors of title element are book element and  bookstore element:
<bookstore>
  <book>
  <title>Harry Potter</title>
  <year>2005</year>
</book>
</bookstore>
Descendants of bookstore element
are the book, title, author, year,
and price elements:

XPath Syntax
• XPath uses path expressions to select nodes in an XML document
• Node is selected by following a path or steps.
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

Example for
Xpath
<bookstore>
<book>
</book>
<book>
  <title lang="en">Learning XML</title>
</book>
</bookstore>
Path Expression Result
bookstore Selects all nodes with the name "bookstore"
/bookstore
Selects the root element bookstore
Note: If the path starts with a slash ( / ) it always
represents an absolute path to an element!
bookstore/book Selects all book elements that are children of bookstore
//book
Selects all book elements no matter where they are in the
document
bookstore//book
Selects all book elements that are descendant of the
bookstore element, no matter where they are under the
bookstore element
//@lang Selects all attributes that are named lang

Predicates
• Used to find a specific node or a node that contains a specific value.
• Predicates are always embedded in square brackets.
/bookstore/book[1]
Selects the first book element that is the child of the bookstore
element.
Note: In IE 5,6,7,8,9 first node is[0], but according to W3C, it is
[1]. To solve this problem in IE, set the SelectionLanguage to
XPath:
In JavaScript: xml.setProperty("SelectionLanguage","XPath");
/bookstore/book[last()]
Selects the last book element that is the child of the bookstore
element

Predicates
/bookstore/book[last()-1]
Selects the last but one book element that is the child of
the bookstore element
/bookstore/book[position()<3]
Selects the first two book elements that are children of
the bookstore element
//title[@lang]
Selects all the title elements that have an attribute
named lang
//title[@lang='en']
Selects all the title elements that have a "lang" attribute
with a value of "en"
/bookstore/book[price>35.00]
Selects all the book elements of the bookstore element
that have a price element with a value greater than
35.00
/bookstore/book[price>35.00]/title
Selects all the title elements of the book elements of the
bookstore element that have a price element with a
value greater than 35.00

Selecting Unknown Nodes
• XPath wildcards can be used to select unknown XML nodes.
• Example:
Wildcard Description
* Matches any element node
@* Matches any attribute node
node() Matches any node of any kind
/bookstore/*
Selects all the child element nodes of the
bookstore element
//* Selects all elements in the document
//title[@*]
Selects all title elements which have at least
one attribute of any kind

Selecting Several Paths
• By using the | operator in an XPath expression you can select several paths.
• Some path expressions and the result of the expressions:
//book/title | //book/price
Selects all the title AND price elements of all book
elements
//title | //price
Selects all the title AND price elements in the
document
/bookstore/book/title | //price
Selects all the title elements of the book element of
the bookstore element AND all the price elements in
the document

Example for Xpath
<bookstore>
<book>
</book>
<book>
</book>
</bookstore>
//book/title | //book/price
Selects all the title AND price elements of all
book elements
//title | //price
Selects all the title AND price elements in the
document
/bookstore/book/title | //price
Selects all the title elements of the book
element of the bookstore element AND all the
price elements in the document

XPath Syntax
• XPath uses path expressions
– To select nodes in an XML document
• Node is selected by following a path or steps.
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

XPath Example
<bookstore>
<book category="cooking">
  <title lang="en">Everyday Italian</title>
  <author>Giada De Laurentiis</author>
  <year>2005</year>
</book>
<book category="children">
  <year>2005</year>
</book>

XPath Example
<book category="web">
  <title lang="en">XQuery Kick Start</title>
  <author>James McGovern</author>
  <author>Per Bothner</author>
  <author>Kurt Cagle</author>
  <author>James Linn</author>
  <author>Vaidyanathan Nagarajan</author>
  <year>2003</year>
</book>
<book category="web">
  <author>Erik T. Ray</author>
  <year>2003</year>
</book>
</bookstore>

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