Re: [netmod] JSON to XML lossy conversion
Ladislav Lhotka <ladislav.lhotka@nic.cz> Fri, 17 July 2020 07:11 UTC
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To: Michal Vaško <mvasko@cesnet.cz>, Carsten Bormann <cabo@tzi.org>
Cc: netmod <netmod@ietf.org>
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From: Ladislav Lhotka <ladislav.lhotka@nic.cz>
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Date: Fri, 17 Jul 2020 09:11:22 +0200
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Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/Nf4ZQYA2KBzwPSWBAO2YR7r5KK4>
Subject: Re: [netmod] JSON to XML lossy conversion
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On 17. 07. 20 8:57, Michal Vaško wrote: > Hi Carsten, > you had an interesting idea to have tools that could warn about these problems (although that is hardly a proper solution) but it is not really possible because the problem may occur whenever there is union with a 'string' and 'int8' - 'int32', 'uint8' - 'uint32', or 'boolean', in any order. Meaning in lots of, if not most, unions. And I have considered only XML and JSON, I have not looked into CBOR, which may make it even worse. What you can do is to define a metadata annotation specifying the union member for a particular instance, and implement it in your tools. This would be a solution independent of instance representation. Lada > > Regards, > Michal > >> >>> In my view, if it is a bug, it is in the design of the union type in YANG - there is no general way to signal the actual union member type for an instance. >> >> Right. The ambiguity is normally not a problem for a type choice (which is just a union of the possible values of all types given), unless what specific alternative was chosen is intended to carry semantics. >> >>> I believe it is a good thing that some encodings allow for at least partial signalling. >>> >>> Note that similar issues may arise even more often in CBOR, see e.g. comments for section 5.12 in >>> >>> https://mailarchive.ietf.org/arch/msg/core/Zrb2yhSSdlouS6PI9qfsA1bsDB4/ >> >> In the original YANG (XML-only), everything was represented as a text string, so the ambiguity was the highest we see now. YANG-JSON and YANG-CBOR provide progressively more disambiguating information, so the interpretation (which chosen alternative) may be different from the one after converting to YANG-XML. >> >> It gets slightly worse if the non-text type has a conversion to text that is not fully nailed down; I don’t know if that is a problem with the current set of YANG types, but any new type could of course worsen the situation. >> >> The onus is now on the author of the YANG module to make sure that the varying levels of ambiguity do not cause a problem. I would be interested to know whether there is any tool support for this. >> >> Grüße, Carsten >> > > > -- Ladislav Lhotka Head, CZ.NIC Labs PGP Key ID: 0xB8F92B08A9F76C67
- [netmod] JSON to XML lossy conversion Michal Vaško
- Re: [netmod] JSON to XML lossy conversion Ladislav Lhotka
- Re: [netmod] JSON to XML lossy conversion Juergen Schoenwaelder
- Re: [netmod] ?==?utf-8?q? JSON to XML lossy conve… Michal Vaško
- Re: [netmod] JSON to XML lossy conversion Carsten Bormann
- Re: [netmod] ?==?utf-8?q? JSON to XML lossy conve… Michal Vaško
- Re: [netmod] JSON to XML lossy conversion Juergen Schoenwaelder
- Re: [netmod] JSON to XML lossy conversion Ladislav Lhotka
- Re: [netmod] JSON to XML lossy conversion Carsten Bormann
- Re: [netmod] JSON to XML lossy conversion Vladimir Vassilev
- Re: [netmod] JSON to XML lossy conversion Ladislav Lhotka
- Re: [netmod] JSON to XML lossy conversion Juergen Schoenwaelder
- Re: [netmod] JSON to XML lossy conversion Ladislav Lhotka
- Re: [netmod] JSON to XML lossy conversion Carsten Bormann