Re: deterministic content model?

[Gary Stephenson <garys@ihug.com.au>]

Hi Rob,

> The reason for this dichotomy is that XML processors are not required to
> analyse the content model to see if it is deterministic *unless* the
> instance document contains an element of that type.  This is my
> understanding of xml 1.0, 3.2.1 [1] which reads:-
>
> "For compatibility, it is an error if an element in the document can match
> more than one occurrence of an element type in the content model."
>
> So, it is only an error if there is an element in the document!?  In the
> case of ibm47v01, there is not a "child4" element, so it is my understanding
> that the processor does not need to build the DFA for its content model.

Yes.  Thanks for that.  Interesting that I read that sentence many times and
was still confused in this instance.  Can't see the woods for the trees
sometimes... <g>

> Our XML Validator used to check every content model to see if it was
> deterministic.  However we changed this when we realised the impact it could
> have on perform when processing very large DTDs.  Normal Walsh's DocBook DTD
> [2] is a good example of a DTD containing many element types, many of which
> are not used by individual instance documents.

I am still trying to get my head around how I would even approach checking for
non-determinism. And I'm unsure whether what you've just told me will actually
make it easier or harder to implement - irrespective of the relative
processing efficiencies.

cheers,

gary