Showing posts with label XML Validation. Show all posts
Showing posts with label XML Validation. Show all posts

Thursday, August 23, 2012

XML Validation

XML with correct syntax is "Well Formed" XML.
XML validated against a DTD is "Valid" XML.

Well Formed XML Documents

A "Well Formed" XML document has correct XML syntax.
The syntax rules were described in the previous chapters:
  • XML documents must have a root element
  • XML elements must have a closing tag
  • XML tags are case sensitive
  • XML elements must be properly nested
  • XML attribute values must be quoted
<?xml version="1.0" encoding="ISO-8859-1"?>
<body>Don't forget me this weekend!</body>

Valid XML Documents

A "Valid" XML document is a "Well Formed" XML document, which also conforms to the rules of a Document Type Definition (DTD):
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE note SYSTEM "Note.dtd">
<body>Don't forget me this weekend!</body>
The DOCTYPE declaration in the example above, is a reference to an external DTD file. The content of the file is shown in the paragraph below.


The purpose of a DTD is to define the structure of an XML document. It defines the structure with a list of legal elements:
<!DOCTYPE note
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT heading (#PCDATA)>
If you want to study DTD, you will find our DTD tutorial on our homepage.

XML Schema

W3C supports an XML-based alternative to DTD, called XML Schema:
<xs:element name="note">

    <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"/>

If you want to study XML Schema, you will find our Schema tutorial on our homepage.

A General XML Validator

To help you check the syntax of your XML files, we have created an XML validator to syntax-check your XML.
Please see the next chapter.