> On 13 Oct 2015, at 12:42, Juergen Schoenwaelder > <j.schoenwael...@jacobs-university.de> wrote: > > On Tue, Oct 13, 2015 at 12:30:58PM +0200, Ladislav Lhotka wrote: >> >>> On 13 Oct 2015, at 12:19, Juergen Schoenwaelder >>> <j.schoenwael...@jacobs-university.de> wrote: >>> >>> On Tue, Oct 13, 2015 at 11:45:30AM +0200, Ladislav Lhotka wrote: >>>> David Reid <r...@snmp.com> writes: >>>> >>>>> section 6.3.1 states: >>>>> >>>>> If a YANG compiler does not support a particular extension, which >>>>> appears in a YANG module as an unknown-statement (see Section 14), >>>>> the entire unknown-statement MAY be ignored by the compiler. >>>>> >>>>> If a YANG parser does not support a particular extension, which >>>>> appears in a YANG module as an unknown-statement (see Section 14), >>>>> the entire unknown-statement MAY be ignored by the parser. Note >>>> >>>> Implications of this statement are still not clear to me. Let's say some >>>> protocol introduces an extension that is critical for that >>>> protocol. Does the above sentence mean that an implementation of that >>>> protocol MAY ignore the extension if it happens to use a parser that >>>> doesn't support it? >>>> >>>> Lada >>>> >>>>> that even in this case the semantics associated with the extension >>>>> still apply (as if they were part of a description statement). >>>>> >>> >>> Did you read the following sentence: >>> >>> [...] Note that >>> even in this case the semantics associated with the extension still >>> apply (as if they were part of a description statement). >> >> Well, if the parser ignores the extension statement, then the application >> has no way to find out that the extension is present to be able to apply its >> semantics. >> > > Description statements have always to be taken into account.
This is a different thing. Such a description would be a substatement to the "extension" (built-in) statement that defines the extension. In order to apply the semantics in appropriate places, an application must see where the extension statement is actually *used*. This is only possible if the underlying parser provides this information. > >>> I think it answers your question with a 'no'. >> >> Specifying behaviour of a YANG parser using 2119 keywords YANG parser >> doesn't make much sense to me, because it all depends on the purpose of the >> application that uses the parser. >> > > I do not get your point. The text says a parser may skip over an > extension it does not know how to process and it says the semantics > still apply as if they were part of a description statement. What > is the problem with this? If a protocol requires an extension to be honoured, then there is no excuse for the parser to ignore it. But the sentence I am objecting to says "MAY ignore" without any qualification. Lada > > /js > > -- > Juergen Schoenwaelder Jacobs University Bremen gGmbH > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > Fax: +49 421 200 3103 <http://www.jacobs-university.de/> -- Ladislav Lhotka, CZ.NIC Labs PGP Key ID: E74E8C0C _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
