Andy Bierman <a...@yumaworks.com> wrote:
> On Wed, Oct 10, 2018 at 6:59 PM, Reshad Rahman (rrahman) <rrah...@cisco.com>
> wrote:
>
> > On 2018-10-10, 9:59 AM, "netmod on behalf of Martin Bjorklund" <
> > netmod-boun...@ietf.org on behalf of m...@tail-f.com> wrote:
> >
> > Ladislav Lhotka <lho...@nic.cz> wrote:
> > > Martin Bjorklund <m...@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.
> > <RR> But that means making non-backwards compatible change to the XML
> > representation?
> >
>
> Not really. It means NETMOD WG would be creating its own special variant of
> XPath.
Not at all. What I propose is perfectly fine, legal XPath 1.0.
XPath 1.0 says that an XPath expression is evaluated in a context.
One item in the context is a set of mappings from <prefix> to <uri>,
where <prefix> is used to lookup prefixes used in the XPath
expression, e.g. in "/foo:interfaces" "foo" is the prefix.
It is perfectly fine to say that the prefix mapping set is this:
"ietf-interfaces" -> "urn:ietf:params:xml:ns:yang:ietf-interfaces"
"ietf-ip" -> "urn:ietf:params:xml:ns:yang:ietf-ip"
and use that to evaluate the expression
/ietf-interfaces:interfaces/ietf-interfaces:interface/ietf-ip/ipv4
/martin
>
>
> > 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.
> >
>
>
> We should avoid making off-the-shelf implementations of standards like
> XPath unusable.
> At the very least this should be only available if the server supports it
> (with a capability URI)
>
>
>
> > <RR> So we need an update to RFC7951?
> >
> > Regards,
> > Reshad.
> >
> >
>
> Andy
>
>
> >
> > /martin
> >
> >
> >
> >
> >
> > >
> > > Lada
> > >
> > > >
> > > > How is this supposed to work with JSON?
> > > >
> > > >
> > > > /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 mailing list
> > netmod@ietf.org
> > https://www.ietf.org/mailman/listinfo/netmod
> >
> >
> > _______________________________________________
> > netmod mailing list
> > netmod@ietf.org
> > https://www.ietf.org/mailman/listinfo/netmod
> >
_______________________________________________
netmod mailing list
netmod@ietf.org
https://www.ietf.org/mailman/listinfo/netmod
