The slides have majority of information regarding XML, DTD & Schema. Very useful for beginners as well as experienced.

1. XML, DTD & SCHEMA
Pradeep Rapolu

2. MODULE 1: XML OVERVIEW

3. Agenda
Introduction to XML
XML Tree
XML Syntax Rules
XML Elements
XML Attributes
XML Namespaces
XML Encoding
XML with CSS

4. Introduction to XML
What is XML?
• XML is a markup language much like HTML
• XML was designed to describe data.
• XML tags are not predefined.
• XML is a W3C Recommendation
XML is not a replacement of HTML
• XML specifies what data is.
• HTML specifies how data looks.
 XML Doesn’t do anything.
 Some code makes use of XML.

5. Advantages of XML:
• XML Separates Data from HTML
• XML Simplifies Data Sharing
• XML Simplifies Data Transport
• XML Simplifies Platform Changes
• Several Internet languages are written in XML.
 XHTML
 XML Schema
 SVG
 WSDL
 RSS

6. XML Tree
• XML documents form a tree structure
• XML documents are made up with
 Elements
 Attributes
 Text

7. XML Syntax Rules
• XML Elements Must Have a Closing Tag
• XML Tags are Case Sensitive
• XML Elements Must be Properly Nested
• XML Documents Must Have a Root Element
• Entity References
• Comments in XML
• XML must be well formed
Valid XML:
<color id=“2”>green</color> <!-- The color is green -->
Invalid XML:
<color id=2>green</Color

8. XML Elements
• XML Element is everything from a start tag to end tag.
• An element can contain
 other elements
 text
 attributes
 or a mix of all of the above.
• XML Elements must follow naming rules.
E.g.:
<country type=“subcontinent”>India</country>
XML Attributes
• Attributes provide additional information about an element.
• XML Attribute Values Must be Quoted
• Avoid attributes – use only to store metadata.
E.g.:
<file type="gif">computer.gif</file>

9. XML Namespaces
• Namespaces – to avoid name conflicts
Syntax:
xmlns:prefix="URI“
Default Namespace:
• Saves from using prefixes in all the child elements
Syntax:
xmlns="namespaceURI“

10. XML Encoding
• XML documents can contain international characters
Syntax:
<?xml version="1.0" encoding="UTF-8"?>
Unicode:
• Unicode is an industry standard for character encoding of text documents
• Unicode has two variants:
 UTF-8
 UTF-16.
• UTF = Universal character set Transformation Format.
• UTF-8 uses 1 byte (8-bits) to represent characters in the ASCII set, and two or
three bytes for the rest.
• UTF-16 uses 2 bytes (16 bits) for most characters, and four bytes for the rest.
• UTF-8 is the default for documents without encoding information.

11. XML with CSS
• XML documents can be formatted with CSS (Cascading Style Sheets)
• Formatting XML with CSS is not the most common method.
• W3C recommends using XSLT instead.

12. Module 2: DTD Overview

13. Agenda
 Introduction to DTD
 DTD Building Blocks
 DTD Elements
 DTD Attributes
 DTD Entities

14. Introduction to DTD
• DTD defines the document structure with a list of legal elements and
attributes.
• The XML document that follows DTD is valid and well formed.
Why DTD?
• With a DTD, each XML file can carry a description of its own format.
• To verify if the XML received from outside world is valid
• To maintain a standard for interchanging data
DTD Declaration Types:
1. Internal DTD Declaration
2. External DTD Declaration

15. 1. Internal DTD Declaration:
• The DTD is declared inside the XML file
Syntax:
<!DOCTYPE root-element [element-declarations]>
2. External DTD Declaration
• The DTD is declared in an external file
• The DTD document is referred to xml document
Syntax:
<!DOCTYPE root-element SYSTEM "filename">

16. DTD Building Blocks
• Per DTD all the XML documents are made up by the following building
blocks
 Elements
 Attribues
 Entities
 PCDATA
 CDATA

17. DTD Elements
• In DTD, elements are declared with an ELEMENT declaration.
Syntax:
<!ELEMENT element-name category>
or
<!ELEMENT element-name (element-content)>
Element Types:
• <!ELEMENT element-name EMPTY>
• <!ELEMENT element-name (#PCDATA)>
• <!ELEMENT element-name ANY>
• <!ELEMENT element-name (child1, child2,…..)>
• <!ELEMENT element-name (child-name)>
• <!ELEMENT element-name (child-name+)>
• <!ELEMENT element-name (child-name*)>
• <!ELEMENT element-name (child-name?)>
• <!ELEMENT element-name (child1, child2, (child3|child4))>
• <!ELEMENT element-name (#PCDATA|child1|child2|child3|child4)*>

18. DTD Attributes
• DTD, attributes are declared with an ATTLIST declaration.
Syntax:
<!ATTLIST element-name attribute-name attribute-type attribute-value>
Attribute Values:
• <!ATTLIST element-name attribute-name attribute-type default-value>
• <!ATTLIST element-name attribute-name attribute-type #REQUIRED>
• <!ATTLIST element-name attribute-name attribute-type #IMPLIED>
• <!ATTLIST element-name attribute-name attribute-type #FIXED "value">
• <!ATTLIST element-name attribute-name (en1|en2|..) default-value>

19. DTD Entities
• Entities are like variables
• Entities can be declared internal or external
1. Internal Entity Declaration:
Syntax:
<!ENTITY entity-name "entity-value">
2. External Entity Declaration:
Syntax:
<!ENTITY entity-name SYSTEM "URI/URL">
Entity reference in XML document:
<element-name>&entity-name;</element-name>

20. Module 3: XML Schema Overview

21. XML Schema
• XML schema describes the structure of an XML document.
• XSD - XML Schema language
What is an XML Schema?
• XML Schema defines the legal building blocks of an XML document.
An XML Schema -
 defines elements that can appear in a document
 defines attributes that can appear in a document
 defines which elements are child elements
 defines the order of child elements
 defines the number of child elements
 defines whether an element is empty or can include text
 defines data types for elements and attributes
 defines default and fixed values for elements and attributes

22. Advantages of XML Schema over DTD
• XML Schemas are written in XML
• XML Schemas support data types
• XML Schemas support namespaces
XML Schema Syntax:
• The XML Schema must be embedded inside the root element <schema>
<?xml version="1.0"?>
<xs:schema>
...
...
</xs:schema>
XML With XSD:
• XML documents refer XML Schema. (XSD Documents)

23. Agenda
 XML Schema
 XSD Simple Types
 XSD Complex Types
 XSD Complex Types – Indicators
 XSD Complex Types - any & anyAttribute
 XSD Complex Types - Element Substitution
 Writing XML Schema
 XSD Data types

24. XSD Simple Types
• The Simple Types in XSD are –
 Simple Element
 Attribute
1. Simple Element:
• Element contains only text, but no other elements or attributes.
Syntax:
<xs:element name=“element-name" type=“element-type"/>
• Simple elements can have default and fixed values
• XML Schema has a lot of built-in data types. The most common types are:
 xs:string
 xs:decimal
 xs:integer
 xs:boolean
 xs:date
 xs:time

25. 2. Attribute:
• Simple elements cannot have attributes.
• The attribute itself is a simple type.
Syntax:
<xs:attribute name=“attribute-name" type=“attribute-type"/>
E.g.:
<lastname lang="EN">Smith</lastname> <!--Element with Attribute -->
<xs:attribute name="lang" type="xs:string"/> <!-- Attribute definition -->
XSD Restrictions/Facets:
• Restrictions define acceptable values for XML elements or attributes.
• Restrictions on XML elements are called facets.
Different Restrictions:
• Restrictions on Values
• Restrictions on set of values
• Restrictions on a Series of Values
• Restrictions on Whitespace Characters
• Restrictions on Length

26. XSD Complex Types
• A complex type element contains other elements and/or attributes.
• There are four kinds of complex elements -
 empty elements
 elements that contain only other elements
 elements that contain only text
 elements that contain other elements, attributes and text
** The Complex Type Elements can be Extended or Restricted
 Empty elements:
• An empty complex element cannot have contents, but only attributes.
E.g.: <product prodid="1345" />
** By giving complexType element a name and let the element have a type
attribute that refers to the name of the complexType several elements can
refer to the same complex type

27.  Elements that contain only other elements:
• An "elements-only" complex type contains an element that contains only
other elements.
E.g.: <person>
<firstname>John</firstname>
<lastname>Smith</lastname>
</person>
 Elements that contain only text:
• A complex text-only element can contain text and attributes.
E.g.: <shoesize country="france">35</shoesize>
• This type contains only simple content (text and attributes)
• We add a simpleContent element around the content.

28.  Elements that contain other elements, attributes and text (Mixed):
• A mixed complex type element can contain attributes, elements, and text.
E.g.: <letter id=“123”>
Dear Mr.<name>John Smith</name>.
Your order <orderid>1032</orderid>
will be shipped on <shipdate>2001-07-13</shipdate>.
</letter>

29. XSD Complex Types - Indicators
• We can control HOW elements are to be used in documents with indicators.
• There are seven indicators classified into 3 types
a) Order indicators:
• Order indicators define the order of the elements.
 All: The child elements can appear in any order, but must occur
only once:
 Choice: Either one child element or another can occur, but not both
 Sequence: The child elements must appear in a specific order
b) Occurrence indicators:
• Occurrence indicators define the no. of times an element can appear
 maxOccurs: Maximum number of times an element can occur
 minOccurs: Minimum number of times an element can occur

30. c) Group indicators:
• Group indicators define related sets of elements.
 Element Groups:
• Define related sets of elements
• Element groups are defined with the group declaration.
Syntax:
<xs:group name="groupname">
...
</xs:group>
 Attribute Groups:
• Define related sets of attributes.
• Attribute groups are defined with the attributeGroup declaration
Syntax:
<xs:attributeGroup name="groupname">
...
</xs:attributeGroup>

31. XSD Complex Types - any & anyAttribute
any Element:
• The <any> element enables us to extend the XML document with elements not
specified by the schema!
anyAttribute Element:
• The <anyAttribute> element enables us to extend the XML document with
attributes not specified by the schema!

32. XSD Complex Types - Element Substitution
• With Element Substitution one element can substitute another in different
instances
• An attribute “substitutionGroup” used to apply substitution.
• Substitution can be blocked by using attribute block="substitution"

33. Writing XML Schema
• Schemas for XML can be created in below ways
 Hierarchical manner
 Divide the Schema
 Using Named Types

34. XSD Data types
• XSD has below mentioned data types
 String
 Date
 Numeric
 Miscellaneous
Boolean
Binary
AnyURI
Reference:
http://www.w3schools.com