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Re: Potential Erratum Re: clarification on Unique Particle Attribution

From: <sandygao@ca.ibm.com>
Date: Wed, 24 Oct 2001 12:34:34 -0400
To: www-xml-schema-comments@w3.org
Message-ID: <OF1F41AE06.0BE878E4-ON85256AEF.005A8C71@torolab.ibm.com>
Oh, so it's "uniquely determine", not "unique particle". Sorry for having
misunderstood this. But it's hard, isn't it? And I was misled by the
appendix, which only talks about non-group particles, not how to "uniquely
determine" a particle. :-)

Thanks for all your clarification.

Sandy Gao
Software Developer, IBM Canada
(1-905) 413-3255

                    c.uk (Henry S.       To:     Sandy Gao/Toronto/IBM@IBMCA                                       
                    Thompson)            cc:     www-xml-schema-comments@w3.org                                    
                                         Subject:     Potential Erratum Re: clarification on Unique Particle       
                    10/24/2001            Attribution                                                              
                    12:24 PM                                                                                       
                    Please respond                                                                                 
                    to ht                                                                                          

sandygao@ca.ibm.com writes:

> I don't think the following two <choice> declarations are the same, and
> result in the same content model.
>   <group name="grp">
>     <sequence>
>       <element name="e"/>
>     </sequence>
>   </group>
>   <choice>
>     <group ref="grp"/>
>     <group ref="grp" maxOccurs="3"/>
>   </choice>
> and
>   <choice>
>    <sequence>
>      <element name="e"/>
>    </sequence>
>    <sequence max='3'>
>      <element name="e"/>
>    </sequence>
>   </choice>
> Let's follow the spec, and see which particles are involved in the above
> two cases:
> In the first one, there are 4 particles: one for the local element (call
> PE), one for the sequence in the group (PG), one for the first group
> reference (PG1), and one for the second group reference (PG2).

The latter two share a term, namely the sequence model group.

> When we see
> an instance "e", we always use the same element particle PE to validate
> so this particle can be uniquely determined. But we can't determine
> to use PG1 or PG2. I don't see how UPA applies here.

You said it -- we can't distinguish between PG1 and PG2, so UPA _does_

We should be more careful to distinguish terms from particles, I agree.

> In the second one, there are also 4 particles: one for the first sequence
> (PS1), one for the first local element (PE1), and the same for the second
> sequence and local element (PS2 and PE2). Now for "e" in the instance, we
> can't uniquely determine which sequence or element particle to use, hence
> it's a violation of UPA.

You're right, they're _not_ the same -- identity in one case, not in
the other.

> It seems that you are assuming that when a group is referenced by
> places, you'll create different trees of particles for each reference.
> in the first case, you'll get two different element particles as the
> of group reference. But this is not what the spec says. "the particle is
> the particle of ..." is what's mentioned in spec, not "the particle is a
> copy of the particle of ...".

You're right, I should have been more careful in my language.

I also agree, the example you cite is not unambiguously handled by the
spec. as it stands, except in the second (non-normative) formulation
in Appendix H (the one expressed in terms of FSAs).

My personal inclination is to say that in the phrase 'uniquely determining
particle' the intent was that the 'uniquely' goes with the
'determining', not the 'particle', so the fact that there are two
routes to the same particle means you lose, but that's not up to me to
decide -- erratum, please!

Here's why this _should_ be covered by the UPA:

   <group ref="grp"/>
   <element ref="a"/>
   <group ref="grp"/>
   <element ref="b"/>

  Henry S. Thompson, HCRC Language Technology Group, University of
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
               Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
                          URL: http://www.ltg.ed.ac.uk/~ht/
Received on Wednesday, 24 October 2001 12:35:42 UTC

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