From: netmod <[email protected]> on behalf of Martin Björklund <[email protected]> Sent: 22 February 2021 10:13
Juergen Schoenwaelder <[email protected]> wrote: > Thanks Martin, > > so you are saying that > > int8 { range "1..10"; } > > is indeed different from > > uint8 { range "1..10"; } > > and > > int32 { range "1..10"; } Yes. > The use of the word "syntax" in the text you quote may be a left-over > from SMIv2 times [That's what I thought as well, but I couldn't find it in the SMIv2 RFCs. Perhaps it was from some sming text?] <tp> When asked about SNMP/SMI, I always say to start with RFC1155/1156/1157. Either of the first two gives, for me, a clear exposition of the meaning of 'syntax' which I have always taken as read in YANG. Going back, well, ASN.1, ISO etc etc Tom Petch > , it does not really seem to be aligned with how the > term 'syntax' is used elsewhere in RFC 7950. Anyway, if the agreement > back then was that you can't change base types (regardless of type > restrictions), it would have been nice if the text would say this more > clearly. Agreed. /martin > > /js > > On Mon, Feb 22, 2021 at 10:49:38AM +0100, Martin Björklund wrote: > > Hi, > > > > Section 11 of RFC 7950 says: > > > > o A "type" statement may be replaced with another "type" statement > > that does not change the syntax or semantics of the type. For > > example, an inline type definition may be replaced with a typedef, > > but an int8 type cannot be replaced by an int16, since the syntax > > would change. > > > > If we're just considering XML, then the syntax or encoding wouldn't > > change if we went from > > > > type int64 { range "2..4"; } > > > > to > > > > type string { pattern "2|3|4"; } > > > > or > > > > type enumeration { > > enum 2; > > enum 3; > > enum 4; > > } > > > > or > > > > type union { > > type uint8 { range "2"; } > > type string { pattern "3"; } > > type enumeration { enum 4; } > > } > > > > > > But I don't think this is reasonable, and not the intention. I think > > that changing the base built-in type always should be considered > > non-backwards compatible (which the quoted text above seems to imply). > > > > > > /martin > > > > > > > > > > Juergen Schoenwaelder <[email protected]> wrote: > > > On Fri, Feb 19, 2021 at 10:32:34PM +0100, Carsten Bormann wrote: > > > > > > > > > > > > > On 2021-02-19, at 19:18, Juergen Schoenwaelder > > > > > <[email protected]> wrote: > > > > > > > > > > I think the CBOR encoding picks different tags depending on the > > > > > signedness of the base type and this is why things are not that simple > > > > > anymore. > > > > > > > > (This is not the CBOR encoding, but the COMI encoding of keys in URIs.) > > > > > > OK. The CBOR document indeed says: > > > > > > 6.1. The unsigned integer Types > > > > > > Leafs of type uint8, uint16, uint32 and uint64 MUST be encoded using > > > a CBOR unsigned integer data item (major type 0). > > > > > > 6.2. The integer Types > > > > > > Leafs of type int8, int16, int32 and int64 MUST be encoded using > > > either CBOR unsigned integer (major type 0) or CBOR negative integer > > > (major type 1), depending on the actual value. > > > > > > This means the type 'int8 { range 0..10; }' leads to the same > > > encodings as the type 'uint8 { range 0..10; }'. > > > > > > > > For the XML and JSON encodings, all definitions lead to the > > > > > same on-the-wire representation, hence the difference is more an > > > > > implementation detail. I have no clue what the gnmi people do. The > > > > > more diverse encodings we add, the more complex things get. > > > > > > > > Well, if the equivalence expectation that I was trying to describe > > > > actually is ingrained, then whoever designs an encoding (COMI for its > > > > URI encoding included) needs to respect it. That would be important to > > > > know. > > > > > > > > > > Exactly. I think we never defined this. And of course, this can get > > > even more fun if you consider string based encodings. The type > > > > > > type string { pattern "1|2|3|4"; } > > > > > > yields the same _XML encoded_ value space as > > > > > > type int32 { range "1..4"; } > > > > > > but as far as I recall the JSON/CBOR encodings will treat these two > > > differently. So yes, ideally the YANG language would have clear rules > > > what YANG's type equivalences are. > > > > > > /js > > > > > > -- > > > Juergen Schoenwaelder Jacobs University Bremen gGmbH > > > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > > > Fax: +49 421 200 3103 <https://www.jacobs-university.de/> > > > > > > _______________________________________________ > > > netmod mailing list > > > [email protected] > > > https://www.ietf.org/mailman/listinfo/netmod > > -- > Juergen Schoenwaelder Jacobs University Bremen gGmbH > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > Fax: +49 421 200 3103 <https://www.jacobs-university.de/> _______________________________________________ netmod mailing list [email protected] https://www.ietf.org/mailman/listinfo/netmod _______________________________________________ netmod mailing list [email protected] https://www.ietf.org/mailman/listinfo/netmod
