xml-dev - Re: Notations

[Arjun Ray <aray@q2.net>]

On Thu, 25 Jun 1998, John Cowan wrote:

> Simon St.Laurent wrote:
> 
> > 2.5 Notation Declarations
> > 
> > Notation declarations are made with XSC:Notation elements nested in the
> > XSC:XSchema element.
> > 
> > <!ELEMENT XSC:Notation (Doc?, ((PubidLiteral, SystemLiteral?) |
> > SystemLiteral))>
> > [...]
> > 
> > Notations may include either a Public Identifier and an optional system
> > literal, or just a system literal.
> 
> Confusing way to put it.  Notations may include a pubid or a sysid
> or both in that order.  The formal content model is phrased the way
> it is -- Ron's draft used
> 
>         (PubidLiteral | SystemLiteral | (PubidLiteral, SystemLiteral))
> 
> -- just to avoid SGML ambiguity.

Unfortunately, this content model is the ambiguous one!

===
[test]$ cat ambig
<!doctype ambig [
<!element   ambig
            - -
            (p | s | (p, s))
            >
<!element   (p,s)
            - -
            (#PCDATA)
            >
]>
[test]$ nsgmls -s ambig
nsgmls:ambig:5:28:E: content model is ambiguous: when no tokens have been
matched, both the 1st and 2nd occurrences of "P" are possible
nsgmls:ambig:12:1:E: no document element
[test]$
===

I think Simon has it right in terms of the content model, while your
statement (one or the other or both in order) is a clearer formulation in
English. Blame this on the ambiguity rules!:)


Arjun



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