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:

    Internal DTD

    This is an XML document with a Document Type Definition: 
    <?xml version="1.0"?>
<!DOCTYPE note [
  <!ELEMENT note    (to,from,heading,body)>
  <!ELEMENT to      (#PCDATA)>
  <!ELEMENT from    (#PCDATA)>
  <!ELEMENT heading (#PCDATA)>
  <!ELEMENT body    (#PCDATA)>
]>
<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):

    External DTD

    This is the same XML document with an external DTD:  
    <?xml version="1.0"?>
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

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