Re: [pointless:Partiles:Structure]: i cannot understand this phrase...

"choi jongwon" <jwchoi@digiweb21.com> writes:

> this question is about pointless of Partiles in Structure spec.
> 
> 3.9.6
>  ...
>  Schema Component Constraint: Particle Valid(Restriction)
>  ...
>  ...
>  <choice> 
>   One of the following must be true: 
>   2.2.1 {particles} is empty "and the particle within which this <choice> appears has {min occurs} of 0. "
>   2.2.2 All of the following must be true: 
>    2.2.2.1 The particle within which this <choice> appears has {max occurs} and {min occurs} of 1.
>    2.2.2.2 One of the following must be true: 
>     2.2.2.2.1 The <choice>'s {particles} has only one member. 
>     2.2.2.2.2 The particle within which this <choice> appears is itself among the {particles} of a <choice>. 
> 
>  in above 2.2.1,
>  i cannot understand why "and the particle within which this <choice> appears has {min occurs} of 0." is appended... 
> "{particles} is empty" is not enough?.. 

Because <choice/> is unsatisfiable.  It's like AND and OR considered
as n-ary functions:

  AND() is true ; including <sequence/> as a required part of a
                  content model does not change what it validates

  OR() is false ; including <choice/> as a required part of a content
                  model ensures that it never validates anything

So for <choice/> to be pointless, it must be optional.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
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Received on Saturday, 7 July 2001 10:20:13 UTC