Re: [netmod] xpath expressions in JSON

Ladislav Lhotka <lhotka@nic.cz> wrote:
> Martin Bjorklund <mbj@tail-f.com> writes:
> 
> > Hi,
> >
> > While reviewing restconf-notif, I saw this example:
> >
> >    {
> >       "ietf-subscribed-notifications:input": {
> >          "stream": "NETCONF",
> >          "stream-xpath-filter": "/ds:foo/",
> >          "dscp": "10"
> >       }
> >    }
> >
> > Note the "stream-xpath-filter".  It has a prefix in the XPath string.
> > How are prefixes declared when JSON is used?
> >
> > The leaf "stream-xpath-filter" says:
> >
> >               o  The set of namespace declarations are those in scope on
> >                  the 'stream-xpath-filter' leaf element.
> >
> > (I think I provided that text...)
> >
> > This assumes that the encoding is XML, or at leas that the encoding
> > can somehow transfer namespace declarations.
> 
> It can't. There are two options:
> 
> 1. have different representations of this value in XML and JSON,
>    analogically to instance indentifiers (sec. 6.11 in RFC 7951).
> 
> 2. use a module name rather than a prefix in XML, too.
> 
> I would suggest #2.

Hmm, so you mean change the leaf "stream-xpath-filter" to say:

         o  The set of namespace declarations has one member for each
            YANG module supported by the server.  This member maps
            from the YANG module name to the YANG module namespace.

            This means that in the XPath expression, the module name
            serves as the prefix.

... and then also give an example of this.

This is probably what we need to do in all places where yang:xpath1.0
is used, going forward.  Maybe even define a new type
yang:xpath1.0-2 (name?) with the set of namespace declarations
built-in.

/martin

> 
> Lada
> 
> >
> > How is this supposed to work with JSON?
> >
> >
> > /martin
> >
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> > https://www.ietf.org/mailman/listinfo/netmod
> 
> -- 
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
> 