Re: choice group particel whose {particles} is empty

"Stanley Guan" <stanley.guan@oracle.com> writes:

> My main question is how useful choice B is?  Is it main use
> is like what I said -- "negative particle"?

Yes, but although that's the only _use_ one can imagine, that's not
why we allowed it -- rather because it seemed on balance better to
keep all the groups consistent, and allow no particles, than to
special-case <choice>.

The analogy I usually refer to is that and() (that is, boolean 'and',
no arguments) is always true, but or() is always false.  Compare
<sequence/> and <choice/>.

> > If you mean that a complex type definition which _has_ such a choice
> > as its content model is emptiable, then yes,
> >  A ---> emptiable, B -x-> emptiable
> 
> Yes, this is what I mean.

Good, then I think that's all clarified.

ht
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  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
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Received on Thursday, 26 September 2002 13:10:45 UTC