Singletons in a DTD

Joshua E. Smith jesmith at
Fri May 14 02:55:34 BST 1999

At 11:37 AM 5/13/99 -0700, David LeBlanc wrote:
>Would (S1? | S2? | S3? | (C1 | C2 | C3)*) work?

Nope.  That would allow only one of S1, S2, or S3.  I need to allow up to
one of each, in any order.

As was pointed out in a separate, but coincidentally related, thread, you'd
have to put a * at the end of that, which suddenly loses singletonness.  Alas.

But I guess the & syntax from SGML is deceptively simple.  I don't
completely follow that other thread, but I gather it's hard to implement
which is probably why they left it out of XML.

-Joshua Smith

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