Re: [netmod] xpath expressions in JSON
Martin Bjorklund <mbj@tail-f.com> Mon, 22 October 2018 12:56 UTC
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Date: Mon, 22 Oct 2018 14:56:05 +0200
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To: lhotka@nic.cz
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From: Martin Bjorklund <mbj@tail-f.com>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/7F37aLvHjYCBL8qf4gkHjiUIn60>
Subject: Re: [netmod] xpath expressions in JSON
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Ladislav Lhotka <lhotka@nic.cz> wrote: > Martin Bjorklund <mbj@tail-f.com> writes: > > > Hi, > > > > Going back to the most urgent issue, what is this WG's recommendation > > for the subscribed-notifications draft in NETCONF wrt/ their usage of > > yang:xpath1.0 in filters? > > > > To summarize: > > > > We already have > > > > o instance-identifier in XML uses prefixes from the XML document > > o instance-identifier in JSON uses module names as prefixes > > o XPath in NETCONF filter uses prefixes from the XML document > > o XPath in JSON query filter uses module names as prefixes > > > > > > Alternative A: > > -------------- > > > > Use different encodings for "stream-xpath-filter" as well, depending > > on if it is XML or JSON. > > > > We would do in SN: > > > > o If the node is encoded in XML, the set of namespace > > declarations are those in scope on the > > 'stream-xpath-filter' leaf element. > > > > o If the node is encoded in JSON, the set of namespace > > declarations is the set of prefix and namespace pairs > > for all supported YANG modules, where the prefix is > > Is "supported" the same as "implemented", or something else? It should be "implemented". > > the YANG module name and the namespace is as defined > > by the "namespace" statement in the YANG module. > > > > Pro: the format is consistent within each encoding. > > > > Con: unclear how to handle other encodings. > > Con: we keep using context-depending encodings. > > Con: XPath expressions in JSON can get pretty long (I assume it's not > just an instance identifier but may contain predicates etc.). We > cannot use the trick with the default namespace as in YANG, so all > data node names will have to carry the prefix. Yes. > > We could probably add that CBOR uses the same representation as JSON. > > > > Example in XML: > > > > <stream-xpath-filter > > xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces" > > xmlns:ip="urn:ietf:params:xml:ns:yang:ietf-ip"> > > /if:interfaces/if:interface/ip:ipv4 > > </stream-xpath-filter> > > > > Example in JSON: > > > > "stream-xpath-filter": > > "/ietf-interfaces:interfaces/ietf-interfaces:interface/ietf-ip:ipv4" > > > > > > > > Alternative B: > > -------------- > > > > Use a non-context depending encoding, with the module name as prefix. > > > > We would do in SN: > > > > o The set of namespace > > declarations is the set of prefix and namespace pairs > > for all supported YANG modules, where the prefix is > > the YANG module name and the namespace is as defined > > by the "namespace" statement in the YANG module. > > > > Pro: the format is independent from the protocol encoding > > > > Con: in XML, this leaf is treated differently from other XPath > > expressions, such as get-config filter and nacm rules. > > > > Example in XML: > > > > <stream-xpath-filter> > > /ietf-interfaces:interfaces/ietf-interfaces:interface/ietf-ip:ipv4 > > </stream-xpath-filter> > > > > Example in JSON: > > > > "stream-xpath-filter": > > "/ietf-interfaces:interfaces/ietf-interfaces:interface/ietf-ip:ipv4" > > > > > > My proposal is A. I think it is more important with consistency > > within each encoding than across encodings. > > I would suggest to consider declaring prefixes & namespaces explicitly > in the data, as in the schema mount document. It is independent of > encoding and the expressions can be kept short. In fact, one of the > namespaces can be declared as default, so this use of XPath would then > be very similar to YANG. Ok, so this is another alternative that works today, and achieves the goal of being encoding-independent. It is still context-dependent though. BTW, when used in filters, it is nice to let an unprefixed name to match any namespace; i.e., treat "foo" as syntactic sugar for "local-name(.) = 'foo'". ("*:foo" is not legal...) /martin > > Lada > > > > > (This said, I would like to have a context-independent encoding of all > > YANG types in the future. But not now.) > > > > > > > > > > /martin > > > > _______________________________________________ > > netmod mailing list > > netmod@ietf.org > > https://www.ietf.org/mailman/listinfo/netmod > > -- > Ladislav Lhotka > Head, CZ.NIC Labs > PGP Key ID: 0xB8F92B08A9F76C67 >
- [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Reshad Rahman (rrahman)
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Qin Wu
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Vladimir Vassilev
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Vladimir Vassilev
- Re: [netmod] xpath expressions in JSON Vladimir Vassilev
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Reshad Rahman (rrahman)
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Reshad Rahman (rrahman)
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Reshad Rahman (rrahman)
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Vladimir Vassilev
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Reshad Rahman (rrahman)
- Re: [netmod] xpath expressions in JSON Vladimir Vassilev
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Juergen Schoenwaelder
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Juergen Schoenwaelder
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Andy Bierman
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Qin Wu
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Juergen Schoenwaelder
- Re: [netmod] xpath expressions in JSON Robert Wilton
- Re: [netmod] xpath expressions in JSON Juergen Schoenwaelder
- Re: [netmod] xpath expressions in JSON Ladislav Lhotka
- Re: [netmod] xpath expressions in JSON Juergen Schoenwaelder
- Re: [netmod] xpath expressions in JSON Martin Bjorklund
- Re: [netmod] xpath expressions in JSON Kent Watsen