ModSAX: Proposed Core Features

Simon St.Laurent simonstl at
Fri Mar 12 18:18:02 GMT 1999

At 12:12 PM 3/12/99 -0500, John Cowan wrote:
>Simon St.Laurent wrote:
>>    Requires the parser to load the external subset of the DTD and process
>> it.  (External parameter entities remain a separate issue referenced by a
>> separate feature.)
>I don't see why it should be.  I think that parsers will either
>process just the internal subset, or will load all external DTD
>parts, including both the external subset and the external
>parameter entities.  (Ignoring the internal subset is *not* an
>option, of course, except for DPH parsers.)

I suppose it doesn't _have_ to be, and David's message earlier this morning
combined them.  (I wrote my message before I got his message.)

Still, I can imagine that it might well be useful to privilege the external
subset's initial contents, without retrieving stacks of validation
information stored in external parameter entities.  An XLink application,
for example, might not care about retrieving and analyzing lots of element
declarations when all it really needs is the attribute declarations for
defaulting.  A mechanism like this might be useful in such a context - put
attribute declarations in the ext subset, element declarations in a file
referenced by PEs, and go.  Validating parsers would get all of it, while
non-validating parsers could pick out the parts they need. You could do the
same thing with the internal subset, but frankly I'd rather not use the
internal subset for anything I can avoid - management of an external subset
is _much_ easier.

(I don't think the spec is clear on whether a non-validating parser that
has read the external subset is then required to go get PE values; I
suspect it doesn't have to.)

The example may feel a little far-fetched.  In any case, it's an argument
for keeping features described in different parts of the spec, which seems
to me like a good way to proceed in general.

Simon St.Laurent
XML: A Primer / Building XML Applications (April)
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