XML Torture Test: Parsers Fail

Richard L. Goerwitz richard at goon.stg.brown.edu
Wed Apr 7 15:37:51 BST 1999

Chris Olds wrote:
> I'm not so sure that IE5 is wrong in reporting an error (when unreferenced
> General Entities are DTD chunks).  The XML REC says (in 4.3.2 "Well-Formed
> Parsed Entities")
>> "An external general parsed entity is well-formed if it matches the
>> production labeled extParsedEnt", which is an optional TextDecl [77]
>> followed by 'content' [43].  Non-validating processors are not required to
>> read external entities, but they are not forbidden to read them if they are
>> not referenced.
> While I don't think this is necessarily the best choice, I think it is just
> that - an implementation choice.

I don't see anything in the spec that says "don't read and validate 
external parsed entities if they're not used."  And in fact, the spec
seems to say that, in order to be valid, they must (whether used or not)
match certain productions in the grammar.

Someone please correct me if there is explicit language to the contrary.

My feeling is that this is another one of those cases where the XML spec
is typically interpreted in terms of SGML practice, but where nothing in
the XML spec itself actually mandates such interpretation.

And in fact, one can make a good case for reading in and checking exter-
nal entities even if they're not "used."  If you fail to do this, you can
end up with a DTD that itself triggers errors when used with some docu-
ments, but not others.  Worse yet, you can end up with a DTD that was
thought to be valid, but which fails unexpectedly when used with a new
document instance.


Richard Goerwitz
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