Re: [netmod] xpath expressions in JSON

Ladislav Lhotka <lhotka@nic.cz> Wed, 10 October 2018 12:40 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: Martin Bjorklund <mbj@tail-f.com>, netmod@ietf.org
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Date: Wed, 10 Oct 2018 14:40:37 +0200
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Subject: Re: [netmod] xpath expressions in JSON
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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.

Lada

>
> How is this supposed to work with JSON?
>
>
> /martin
>
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-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67