Re: [netmod] xpath expressions in JSON

Robert Wilton <rwilton@cisco.com> Thu, 18 October 2018 11:10 UTC

Return-Path: <rwilton@cisco.com>
X-Original-To: netmod@ietfa.amsl.com
Delivered-To: netmod@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 3E5D212D4E9 for <netmod@ietfa.amsl.com>; Thu, 18 Oct 2018 04:10:47 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -14.502
X-Spam-Level:
X-Spam-Status: No, score=-14.502 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cisco.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id DI71mYGshxjf for <netmod@ietfa.amsl.com>; Thu, 18 Oct 2018 04:10:45 -0700 (PDT)
Received: from aer-iport-1.cisco.com (aer-iport-1.cisco.com [173.38.203.51]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 3A70212DD85 for <netmod@ietf.org>; Thu, 18 Oct 2018 04:10:45 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=3331; q=dns/txt; s=iport; t=1539861045; x=1541070645; h=subject:to:references:from:message-id:date:mime-version: in-reply-to:content-transfer-encoding; bh=ioVGWRR4nEISt6r8lfzQ/76rH8kCH97oSwqJelXTX9Q=; b=V5R2bx8qLPdoGJFPSn/v9gGH0dN0imG6HHtRZOqinNzaqtP6BGatCmnH FwQHc4AB61N0cBwrVD7AE+7tp+H06MNSEkEjW/5QTZ3oOtUtx85xi89Lh qWTxr1kAqsBw6qWRXZA5xr/+nYgK1Jb9UU/cbaz1Kp+veQh/FkG/ZAD5h c=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: A0A+AAD5Z8hb/xbLJq1jGQEBAQEBAQEBAQEBAQcBAQEBAQGBZYFbgRBtEiiDdYh2jUmZCQ0YC4QDRgKFIDgWAQMBAQIBAQJtHAyFOgEBAQMBASEVNhsLDgoCAiYCAicwBgEMBgIBAYMcAYIBD6YGgS6FOoRlBYELilmBQT+BESeCa4MbAQGEZIJXAohlBIVZQI82CZBhBheJLoZ5kAqGOoFaIYFVMxoIGxU7gmyCJhd8AQuHU4U/PjCLDQEB
X-IronPort-AV: E=Sophos;i="5.54,396,1534809600"; d="scan'208";a="7339568"
Received: from aer-iport-nat.cisco.com (HELO aer-core-1.cisco.com) ([173.38.203.22]) by aer-iport-1.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Oct 2018 11:10:42 +0000
Received: from [10.63.23.63] (dhcp-ensft1-uk-vla370-10-63-23-63.cisco.com [10.63.23.63]) by aer-core-1.cisco.com (8.15.2/8.15.2) with ESMTP id w9IBAfDw030463; Thu, 18 Oct 2018 11:10:42 GMT
To: Martin Bjorklund <mbj@tail-f.com>, netmod@ietf.org
References: <20181011.181150.1840683183107627057.mbj@tail-f.com> <329f67ff-0774-0fd7-f630-7a01c7e7d3be@cisco.com> <20181012.103727.731509761734796510.mbj@tail-f.com> <20181018.123036.731934458688841323.mbj@tail-f.com>
From: Robert Wilton <rwilton@cisco.com>
Message-ID: <85d40a83-5dfc-a651-e4f1-1c65035704dc@cisco.com>
Date: Thu, 18 Oct 2018 12:10:41 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1
MIME-Version: 1.0
In-Reply-To: <20181018.123036.731934458688841323.mbj@tail-f.com>
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Transfer-Encoding: 7bit
Content-Language: en-US
X-Outbound-SMTP-Client: 10.63.23.63, dhcp-ensft1-uk-vla370-10-63-23-63.cisco.com
X-Outbound-Node: aer-core-1.cisco.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/netmod/Aze71mcRV3oHdSBNwSquOBdurwc>
Subject: Re: [netmod] xpath expressions in JSON
X-BeenThere: netmod@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: NETMOD WG list <netmod.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/netmod>, <mailto:netmod-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/netmod/>
List-Post: <mailto:netmod@ietf.org>
List-Help: <mailto:netmod-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/netmod>, <mailto:netmod-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 18 Oct 2018 11:10:47 -0000

Given where we are, I also agree that A is the better choice.

I would also like to have a context-independent encoding of all YANG 
types in the future.

Thanks,
Rob


On 18/10/2018 11:30, Martin Bjorklund wrote:
> 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
>         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.
>
> 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.
>
> (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
> .
>