Hi Rob,
From: "Robert Wilton -X (rwilton - ENSOFT LIMITED at Cisco)" <rwil...@cisco.com>
Date: Thursday, October 11, 2018 at 11:56 AM
To: "Reshad Rahman (rrahman)" <rrah...@cisco.com>
Cc: Martin Bjorklund <m...@tail-f.com>, "netmod@ietf.org" <netmod@ietf.org>
Subject: Re: [netmod] xpath expressions in JSON
<trimmed>
Yet the examples in section 8.3.6 don't seem to use namespace prefixes in very
many places, e.g. why is it "/example-mod:event1/name='joe'" and not
"/example-mod:event1/example-mod:name='joe'"? Is the example wrong, or
otherwise what am I missing? :-)
<RR> Section 8.3.6 of which document?
RFC 8040.
<RR2> B.3.6, got it. Was looking for 8.3.6, that’s why didn’t find it.
Regards,
Reshad.
Thanks,
Rob
Regards,
Reshad.
Thanks,
Rob
/martin
Thanks,
Rob
There is no standard XPath implementation that can just take an XML
instance document + YANG module and figure out what to do. Custom
code is needed to connect things together. This proposal doesn't
change this.
/martin
A normal XPath implementation will not find any namespace mapping for
the
prefixes.
An XPath expression has no concept of the "current module" inherited
from
the parent
like the JSON encoding. This is problematic for predicates
/ietf-interfaces:interfaces/interface[name='eth0']
XPath says the missing prefixes for 'interface' and 'name' are simply
missing (no namespace).
The JSON encoding says "ietf-interfaces" is used for 'interfaces'. and
'interface'.
There is no specification for the 'name' node inside a predicate.
So you must mean the full module name will be used at every node:
/ietf-interfaces:interfaces/ietf-interfaces:interface[ietf-interfaces:name='eth0']
/martin
Andy
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
> >
> > _______________________________________________
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>
> --
> Ladislav Lhotka
> Head, CZ.NIC Labs
> PGP Key ID: 0xB8F92B08A9F76C67
>
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