Between raw and cooked II: Are? DTDs are just for validation

Jonathan Borden jborden at
Thu Apr 1 16:54:16 BST 1999

David Megginson wrote:
>There *is* a potentially nasty problem lurking here: the DTD may
>contain default values for attributes as well as validation

    If DTDs *were* only for validation there would be no issue here. However
DTDs provide additional functionality beyond validation, namely default
attributes and entities. The problem exists in that XML parsers can *choose*
whether or not to validate and in so doing the <em>information content</em>
of the XML document is altered.

    Validation is optional. Says so. Given this, the question becomes: ought
parsers be allowed to expand entities and default attributes with validation
turned off? What problem does this create?

    Perhaps the XML spec should properly specify that:

         *if* a DOCTYPE declaration is present which specifies a DTD then
the document must be validated else the parser must generate an error.
(DOCTYPE declarations would remain optional).

    In this way document authors would be able to properly specify
information content.

Jonathan Borden

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