Non-Validating XML Parsers: Requirements

John Cowan cowan at
Tue Aug 4 20:15:55 BST 1998

Michael Kay wrote:

> Thanks for the reference. I've read it now. I'm relieved to
> discover it does not recommend or assign a meaning to the
> phrase "MAY NOT".

You are correct.  Mea culpa.
> Wherever "MAY NOT" appears in a (so-called) spec, it either
> means "MUST NOT" or it means "MAY OR MAY NOT", which is a
> synonym for "MAY", and which, as I remarked earlier, is
> formally equivalent to omitting the sentence.

I meant the latter: MAY or may not.

> >
> >> I don't much like "may" either. Everything is permitted
> >> unless the specification prohibits it, a sentence whose
> main
> >> verb is "may" therefore says nothing.

[snip my earlier, flippant response]

Seriously, though, what I wrote was not really a spec, but a
clarification of an existing spec.  In that case, MAY is useful,
for it expresses behavior on which the client cannot depend,
but which may be provided.

John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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