Singletons in a DTD

[David LeBlanc]

Would (S1? | S2? | S3? | (C1 | C2 | C3)*) work?

Dave LeBlanc

At 10:40 AM 5/13/99 -0700, Terje Norderhaug wrote:
>At 8:46 AM 5/13/99, Joshua E. Smith wrote:
>>I have an element which can contain 0 or more instances of some element
>>types (call these collections), and 0 or 1 instances of others (call these
>>singletons), and I don't want to contrain the order.
>>
>>If I have collections C1, C2, C3
>>and I have singletons S1, S2, S3
>>
>>And I declare:
>>
>>(S1? , S2? , S3? , (C1 | C2 | C3)*)
>>
>>Then the singletons, if they appear, would have to be in that order and
>>would have to be first.  So that's not what I want.
>>
>>I suppose I could declare some combinatorics:
>>
>>( S1? | S2? | S3? | (S1 , S2)? | (S2 , S1)? | (S1 , S3)? blah blah blah
>>
>>but I'd have to mix in the C1, C2, C3, etc., too, and I have about 8
>>singleton classes, so this would quickly get totally out of control.
>>
>>Am I missing something, or is what I want to describe not really practical
>>in a DTD?  I'm perfectly comfortable leaving the singletonness out of my
>>DTD (my application will detect duplication errors anyway), if that's the
>>only answer.  But if there *is* a way to capture this without waiting for
>>XSchema to be finished, I'd love to hear it!
>
>The AND '&' connector in SGML covered this functionality, but isn't
>included in XML. It can thus easily be described in a DTD, just not an
>*XML* DTD.
>
>
>-- Terje <Terje at in-progress.com> | Media Design in*Progress
>
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>
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