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Date: Wed, 2 Jan 2013 16:24:32 +0000
From: Tony Finch <dot@dotat.at>
To: Dave Crocker <dcrocker@gmail.com>
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Cc: abnf-discuss@ietf.org, Paul Kyzivat <pkyzivat@alum.mit.edu>
Subject: Re: [abnf-discuss] Some thoughts about how to make ABNF more
 convenient to use
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Dave Crocker <dcrocker@gmail.com> wrote:
> On 1/2/2013 7:57 AM, Tony Finch wrote:
> > Dave Crocker <dcrocker@gmail.com> wrote:
> > >
> > > It would need to be able to distinguish among potentially
> > > independent sets of rules, within a spec. We don't currently have a
> > > way to indicate that.
> >
> > Has there ever been any need for it?
>
> Well, ummm, RFC822 had several parsers, such as for addresses versus dates
> versus free-form like Subject.  Applications often need this, I believe.

Hmm, well I would describe those as sub-languages whereas I thought we
were talking about independent languages. But in both cases they can be
defined / identified using the transitive closure from the starting rule,
without revising ABNF.

I can see that rule sets might be useful for importing collections of
low-level rules, like the ABNF core rules.

> What I don't know is whether there will be the community will to pursue it --
> will we see enough operational benefit?

I think a formal import mechanism would be very useful and could be quite
easy to deploy. Adding namespaces will be a lot of work.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
Forties, Cromarty: East, veering southeast, 4 or 5, occasionally 6 at first.
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occasionally poor at first.
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