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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.

A "Well Formed" XML document is a document that conforms to the XML syntax rules that 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 always be quoted

<?xml version="1.0" encoding="ISO-8859-1"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

Valid XML Documents

A "Valid" XML document also conforms to a DTD.

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 "InternalNote.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

XML DTD

A DTD defines the legal elements of an XML document.

The purpose of a DTD is to define the legal building blocks of an XML document. It defines the document structure with a list of legal elements. You can read more about DTD, and how to validate your XML documents in our DTD tutorial.

XML Schema

XML Schema is an XML based alternative to DTD.

W3C supports an alternative to DTD called XML Schema. You can read more about XML Schema in our Schema tutorial.

A General XML Validator

To help you check the syntax of your xml files, we have created this link so that you can syntax-check any XML file.

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