On Tue, Oct 13, 2015 at 9:42 AM, Ladislav Lhotka <lho...@nic.cz> wrote:
> > > On 13 Oct 2015, at 18:19, Andy Bierman <a...@yumaworks.com> wrote: > > > > > > > > On Tue, Oct 13, 2015 at 5:40 AM, Ladislav Lhotka <lho...@nic.cz> wrote: > > > > > 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. > > > > > > I do not want to change YANG wrt/ MAY skip over. > > We have been over this many times. > > > > Conformance to YANG for the extension: NONE > > This includes syntax and semantics. It makes no sense at all (Lada is > right) > > to say the extension semantics apply. They only apply if the tool > supports > > the extension. Conformance to the extension is a different matter. > > > > A generic YANG tool that is NOT claiming conformance to a particular > > external language statement can completely ignore that statement. > > Right, but this is something very different! The current formulation in > 6020bis (a parser MAY ignore) effectively undermines the possibility to > specify strict conformance rules wrt a certain extension in other documents. > > Good. IMO external statements are not part of YANG. External statements should not be used in a way that requires interoperability between 2 or more entities. It should be completely out of scope wrt/ YANG conformance. I strongly object to changing this part of YANG. It is critical that conformance to YANG does not include any external statement semantics at all. A server MUST be able to parse all the tokens in a YANG module. That is all that is required for external statements. Since YANG extensions MUST NOT alter the syntax and semantics of real YANG statements, a tool that only supports the official YANG language statements can safely ignore all external statements.. Lada > > Andy > > > > > > Lada > > > > > > Andy > > > > > > > > /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 > > -- > Ladislav Lhotka, CZ.NIC Labs > PGP Key ID: E74E8C0C > > > > >
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