Do I need to use a validating parser?

John Cowan cowan at
Tue May 4 19:33:31 BST 1999

Joshua E. Smith wrote:

> I suppose that the validation should really be done a priori by the content
> developer using a validating editor, so doing validation in my plugin is
> really unnecessary.  Is that true?

It depends on whether you are going to take action dependent on the
XML you get, in which case validating provides some (but not all)
of the sanity checks you will need.  If you are just going to
display the content (or do something else that can't damage the
user or the client) then there is no real need.

>  I assume it ignores external
> entities, right?  That means I can't rely on putting boilerplate (think C
> #include files) into an external parsed general entity if I go with expat,
> right?

Correct.  Other non-validating parsers do read external entities, though.

> If you were using a programming language which is XML-ish, what XML
> features would you be annoyed to see left out (substitution of entities is
> an obvious one, which I've seen 3DML slammed for)?  Of those features,
> which does expat not do (and therefore I'll have to do in my application,
> or extend expat to do -- three cheers for open source!)?

Expat does everything except read external entities and validate.
Therefore, it doesn't read an external DTD, but it will process
attribute defaults and such from the internal DTD.
John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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