XSD (XML Schema Definition) is used to describe and validate the structure and content of XML data. It provides more powerful capabilities than DTD. XML Schemas support data types, restrictions on elements and attributes, and namespaces. With XML Schema, groups can agree on standards for exchanging data and documents can be verified. XML Schemas use XML syntax, so they can be edited, parsed, and manipulated like any other XML document. The purpose of an XML Schema is to define the legal building blocks of an XML document, such as elements, attributes, and their structure.

1. XSD

2. XSD
 XML Schema is commonly known as XML Schema Definition (XSD)
 Used to describe and validate the structure and the content of XML data
 An XML-based alternative to DTD (more powerful )
o XML Schemas are extensible to additions
o XML Schemas support data types – easier to define restrictions,
validate correctness, convert between data types
o XML Schemas support namespaces
 With XML Schema, independent groups of people can agree on a
standard for interchanging data
 With XML Schema, you can verify data

3. XSD
 An XML-based alternative to DTD (more powerful )
o Don't have to learn a new language
o Can use your XML editor to edit Schema files
o Can use your XML parser to parse Schema files
o Can manipulate Schemas with the XML DOM
o Can transform Schemas with XSLT
 The purpose of an XML Schema is to define the legal building blocks
of an XML document:
o the elements and attributes that can appear in a document
o the number of (and order of) child elements
o data types for elements and attributes
o default and fixed values for elements and attributes

4. XSD Schema Example
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="https://www.w3schools.com"
xmlns="https://www.w3schools.com"
elementFormDefault="qualified">
….
…..
<xs:schema>
 <schema> element is the root element of every XML Schema
 elements and data types that come from the
"http://www.w3.org/2001/XMLSchema" namespace should be
prefixed with xs

5. XSD Example
<xs:element name=“note" >
<xs:complexType>
<xs:sequence>
<xs:element name="to" type="xs:string"/>
<xs:element name="from" type="xs:string"/>
<xs:element name="heading" type="xs:string"/>
<xs:element name="body" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>

6. Referencing XSD Schema
from XML Document
<?xml version="1.0"?>
<note xmlns="https://www.w3schools.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://www.w3schools.com note.xsd">

7. Simple Elements
 xs:string
 xs:decimal
 xs:integer
 xs:boolean
 xs:date
<xs:element name="lastname" type="xs:string"/>
<xs:element name="age" type="xs:integer"/>
<xs:element name="dateborn" type="xs:date"/>
A complex element is an XML element that contains
other elements and/or attributes – sequence can also
be defined
Here are some XML elements:
<lastname>Refsnes</lastname>
<age>36</age>
<dateborn>1970-03-27</dateborn>

8. Default & Fixed Value of Elements
 A default value is automatically assigned to the element when no other
value is specified
<xs:element name="color" type="xs:string" default="red"/>
 A fixed value is automatically assigned to the element, and no other
value can be assigned
<xs:element name="color" type="xs:string" fixed="red"/>
Note: Restriction on content based on data type

9. Examples: Restriction on Values
<xs:element name="age">
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="120"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
<xs:element name="car">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="Audi"/>
<xs:enumeration value="Golf"/>
<xs:enumeration value="BMW"/>
</xs:restriction>
</xs:simpleType>
</xs:element>

10. Default & Fixed Value of Attributes
 A default value is automatically assigned to attributes when no other
value is specified
<xs:attribute name="lang" type="xs:string" default="EN"/>
 A fixed value is automatically assigned to an attribute, and no other
value can be assigned
<xs:attribute name=“lang" type="xs:string" fixed=“EN“
use =“required” />
(Attributes optional by default)

11. Miscellaneous

12. XML Parser and DOM Model
 Before an XML document can be accessed, it must be loaded into an XML
DOM object
 All modern browsers have a built-in XML parser that can convert text
into an XML DOM object, and thereby access and manipulate it

13. Example of Parsing using JS
• <html>
<body>
<p id="demo"></p>
<script>
var text, parser, xmlDoc;
text = "<bookstore><book>" +
"<title>Everyday Italian</title>" +
"<author>Giada De Laurentiis</author>" +
"<year>2005</year>" +
"</book></bookstore>";
parser = new DOMParser();  Parser object created
xmlDoc = parser.parseFromString(text,"text/xml");  XML DOM obj
document.getElementById("demo").innerHTML =
xmlDoc.getElementsByTagName("title")[0].childNodes[0].nodeValue;
</script>
</body>
</html>

14. XMLHttpRequest Object
 All modern browsers have a built-in XMLHttpRequest object to request
data from a server used to:
 Update a web page without reloading the page
 Request data from a server - after the page has loaded
 Receive data from a server - after the page has loaded
 Send data to a server - in the background
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
// Typical action to be performed when the document is
ready:
document.getElementById("demo").innerHTML =
xhttp.responseText;
}
};
xhttp.open("GET", "filename", true);
xhttp.send();

15. Asynchronous Javascript and XML
AJAX just uses a combination of:
A browser built-in XMLHttpRequest object (to request data from a web server)
JavaScript and HTML DOM (to display or use the data)

16. XSLT, XPATH & XQuery
 XSLT is a language for transforming XML documents
 XPath is a language for navigating in XML documents
 XQuery is a language for querying XML documents

17. What is XPATH?
 XPath is a major element in the XSLT standard.
 XPath used to navigate through elements and attributes in an XML
document
 Path expressions to select nodes or node-sets in an XML doc

18. XPATH Expressions
XPATH Expression Result
/bookstore/book[1] Selects the first book element that is the
child of the bookstore element
/bookstore/book[last()] Selects the last book element that is the
child of the bookstore element
/bookstore/book[last() - 1] Selects the last book but one 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
/bookstore/book[price>35.00] Selects all book elements of 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

19. XSLT

20. Viewing XML
 Without any information about how to display the data, the
browsers can just display the XML document as it is.
<?xml version="1.0" encoding="UTF-8"?>
- <note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Meet me this weekend!</body>
</note>
 color-coded elements
 (+) or minus sign (-) to the left of the elements can be
clicked to expand or collapse the element structure

21. Display XML with CSS
<CATALOG>
<CD>
<TITLE>Empire Burlesque</TITLE>
<ARTIST>Bob Dylan</ARTIST>
<COUNTRY>USA</COUNTRY>
<COMPANY>Columbia</COMPANY>
<PRICE>10.90</PRICE> <YEAR>1985</YEAR>
</CD>
<CD>
<TITLE>Hide your heart</TITLE>
<ARTIST>Bonnie Tyler</ARTIST>
<COUNTRY>UK</COUNTRY>
<COMPANY>CBS Records</COMPANY>
<PRICE>9.90</PRICE> <YEAR>1988</YEAR>
</CD>

22. Corresponding CSS
CATALOG {
background-color: #ffffff;
width: 100%;}
CD {
display: block;
margin-bottom: 30pt;
margin-left: 0;}
TITLE {
display: block;
color: #ff0000;
font-size: 20pt;}
ARTIST {
display: block;
color: #0000ff;
font-size: 20pt;}
COUNTRY, PRICE, YEAR, COMPANY {
display: block;
color: #000000;
margin-left: 20pt;}

23. Displaying XML with XSLT
• XSLT (eXtensible Stylesheet Language Transformations) is the
recommended style sheet language for XML
• XSL (eXtensible Stylesheet Language) is a styling language for XML.
• XSLT used to transform XML into HTML, before it is displayed in a
browser:
• Elements and attributes can be added/removed elements to or from
the output file
• One can also rearrange and sort elements, perform tests and make
decisions about which elements to hide and display
• XSLT uses XPath to find information in an XML document

24. XSL
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0“xmlns:xsl="http://www.w3.org/1999/X
SL/Transform">
<xsl:template match="/">
<html>
<body>
<h2>My CD Collection</h2>
<table border="1">
<tr bgcolor="#9acd32">
<th>Title</th>
<th>Artist</th>
</tr>
<xsl:for-each select="catalog/cd">
<tr>
<td><xsl:value-of select="title"/></td>
<td><xsl:value-of select="artist"/></td>
</tr>
</xsl:for-each>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

25. Root Element
• The root element that declares the document to be an XSL style sheet is
<xsl:stylesheet> or <xsl:transform>. Both synonymous
<xsl:transform version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
Or <xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
• To get access to the XSLT elements, attributes and features we must
declare the XSLT namespace at the top of the document. (Version = 1.0)

26. XSLT <xsl:template> Element
• An XSL style sheet consists of one or more set of rules that are called
templates
• A template contains rules to apply when a specified node is matched
• The content inside <xsl:template> element defines some HTML to write
to the output
• match attribute is used to associate a template with an XML element
match="/" associates the template with the root of the XML source
document i.e. Entire document (Use of XPATH)
<xsl:template match="/">

27. <xsl:value-of> Element
• <xsl:value-of> element used to extract the value of an XML element
and add it to the output stream of the transformation
<td><xsl:value-of select="catalog/cd/title"/></td>
<td><xsl:value-of select="catalog/cd/artist"/></td>
• <xsl:for-each> element can be used to select every XML element of a
specified node-set
<xsl:for-each select="catalog/cd">
<tr>
<td><xsl:value-of select="title"/></td>
<td><xsl:value-of select="artist"/></td>
</tr>
</xsl:for-each>

28. Filtering the output
• One can also filter the output from the XML file by adding a criterion to
the select attribute in the <xsl:for-each> element
<xsl:for-each select="catalog/cd[artist='Bob Dylan']">
<tr>
<td><xsl:value-of select="title"/></td>
<td><xsl:value-of select="artist"/></td>
</tr>
</xsl:for-each>
• Legal filter operators are:
• = (equal)
• != (not equal)
• &lt; less than
• &gt; greater than

29. XHTML

30. XHTML
• Extensible Hypertext Markup Language (XHTML) is part of the family of
XML markup languages.
• Mirrors or extends versions of the widely used HTML
• Developed to make HTML more extensible and increase interoperability
with other data formats

31. Syntax vs HTML
• HTML syntax permits some empty elements to be unclosed (e.g.
<input>) , XML does not permit that
• XML is case-sensitive for element and attribute names, while HTML is
not.
• Shorthand features in HTML such s attribute minimization where
attribute values or their quotes may be omitted (e.g. <option selected>
or <option selected=selected>

32. Behaviour vs HTML
• Behavior on parse errors differ. A fatal parse error in XML (such as an
incorrect tag structure) causes document processing to be aborted
• Most content requiring namespaces will not work in HTML
• JavaScript processing is a little different in XHTML - document.write
not available,
• Due to XHTML's case-sensitivity, all CSS selectors become case-sensitive
for XHTML document