Why Validate an XML Document?
A validating parser will check if an XML document references a DTD. If it does, the parser will check the content and structure of the document against the DTD.
It's easy to understand why a processor will refuse to display a document that is not well-formed, but why even bother validating a document against a DTD? If XML documents are designed for use over the Internet, why bother sending along the accessory baggage of a DTD? Why not just display the document?
These are all good questions. If the purpose of XML was just to provide a vehicle for document display, there would be no need to bother with a DTD. However, XML documents are not just vehicles for display. They are vehicles for storing and structuring content. ...