Re: [abnf-discuss] Target audience for ABNF

Carsten Bormann <> Mon, 20 November 2017 06:50 UTC

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From: Carsten Bormann <>
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Date: Mon, 20 Nov 2017 07:50:02 +0100
Cc: Dave Crocker <>,
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To: Paul Kyzivat <>
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Subject: Re: [abnf-discuss] Target audience for ABNF
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> On Nov 20, 2017, at 02:13, Paul Kyzivat <> wrote:
> Dave,
> On 11/19/17 7:54 PM, Dave Crocker wrote:
>> On 11/19/2017 4:19 PM, Paul Kyzivat wrote:
>>> On 11/19/17 4:08 PM, Carsten Bormann wrote:
>>>>> On Nov 19, 2017, at 19:56, Dave Crocker <> wrote:
>>>>> Computers are not the target audience for computer languages.  Human readers are.
>>>> +10k.
>>> I agree that the human audience is of major importance.
>>> But mechanical verifiability of ABNF is also important.
>> I of course do not mean that computers are irrelevant.  However 'verifiability' invokes formal methods and those typically aren't a concern for typical specification efforts.  Machine processing, yes. Mathematical proofs, no.
>> I gather you are claiming otherwise.  I haven't noticed any history of formal verification for IETF-related specifications, so perhaps you have some pointers?
>>> Ideally IdNits would verify ABNF in drafts as a matter of course. IIUC doing so has been included as a requirement for the new tooling. Given the current situation what IdNits can potentially do is very limited.
>> IdNits hardly seems to qualify as 'verification'.  So I'm probably not understanding exactly what problem you are concerned about.  Details?
> I'm not talking about verifying/proving that the ABNF does what was "intended". I'm willing to grant (for purposes of IETF documents) that verifying the ABNF reflects the *intent* is done by the human review process.

Right, but tools like abnfgen can help enormously in this task — the reviewer generates a few matching instances and eyeballs whether they look like what was intended.  Validating a few manually generated instances against the ABNF is the other computer-assisted process in validation.

> I'm simply talking about verifying that the ABNF is entirely well formed, that all rulenames have definitions, and that there are no multiple definitions. (Multiple instances of the same rulename on the left of  an "=“.)

If the YANG people can do validation automatically upon submission, why can’t we?

(That would probably need the XML, with properly marked up [type=“abnf”] artwork elements.  But we could encourage submitting the XML for drafts that cite RFC 5234 normatively.)

Grüße, Carsten