XML Schemas

An XML Schema describes the structure of an XML document. The XML Schema language is also referred to as XML Schema Definition (XSD).

What is an XSD?

1. XSD stands for XML Schema Definition

2. An XML schema is used to define the structure of an XML document.

3. Schemas are successors to DTDs.
4. Schemas are another approch used by the XML parser to validate an XML document.

5. It is a text file with .xsd extension

What XSD defines?

1. Defines elements that can appear in a document.

2. Defines attributes that can appear in a document.

3. Defines the number of child elements and their sequence.

4. Defines whether an element is empty or can include text.

5. Defines data types for elements and attributes.

6. Defines default and fixed values for elements and attributes.

Why Use XML Schemas?
XML Schemas Support Data Types
1. One of the greatest strength of XML Schema is the support for data types.
2. With support for data types:

It is easier to describe allowable document content.
It is easier to validate the correctness of data
It is easier to work with data from a database
It is easier to define data facets(restrictions on data)
It is easier to define data patterns(Data formats)
It is easier to convert data between different data types

DTDs vs XSDs

XML Schema Structure
A simple XML document

<?xml version=”1.0”>
<email>
   <to>Vinod</to>
   <from>Ashok</from>
   <subject>Reminder(Party)</subject>
   <body>Don't forget me this weekend!</body>
</email>

The XML Schema for the above example

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
targetNamespace=”http://www.waytoeasylearn.com”
elementFormDefault=”qualified”>
<xs:element name="email">
   <xs:element name="to" type="xs:string"/>
   <xs:element name="from" type="xs:string"/>
   <xs:element name="subject"  type="xs:string"/>
   <xs:element name="body" type="xs:string"/>
</xs:element>
</xs:schema>

Main XML Schema Data types
General Data Types

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Types representing Dates and Times

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DTD-compatible Types

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XML Schemas Data Types

One of the greatest strength of XML Schemas is the support for data type. An XSD comprises of two kinds of data types.
1.Simple Type
2.Complex Type

About Ashok Kumar
I'm Ashok Kumar Java Developer from Hyderabad, India. I have a Master Degree in Computer Applications from S.R.K.R Engineering College, Bhimavaram. I achieved Gold Medal in my Master Degree. I am a part time blogger. I am passionate to learn the new Technologies. I would like to enhance my skills and share those to others. Every one wants to learn new Technologies in depth but they want to do this by spending more time to get in depth information. My blog may save your time and learn new Technologies in depth and easy way.