Re: [core] [SenML] Multiple values in a measurement

Carsten Bormann <cabo@tzi.org> Fri, 09 November 2018 23:00 UTC

Return-Path: <cabo@tzi.org>
X-Original-To: core@ietfa.amsl.com
Delivered-To: core@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 3B86E12D4F2 for <core@ietfa.amsl.com>; Fri, 9 Nov 2018 15:00:45 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.2
X-Spam-Level:
X-Spam-Status: No, score=-4.2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3] autolearn=ham autolearn_force=no
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 Okkeg9Rrz-7d for <core@ietfa.amsl.com>; Fri, 9 Nov 2018 15:00:44 -0800 (PST)
Received: from mailhost.informatik.uni-bremen.de (mailhost.informatik.uni-bremen.de [IPv6:2001:638:708:30c9::12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 95FC712D4E7 for <core@ietf.org>; Fri, 9 Nov 2018 15:00:43 -0800 (PST)
X-Virus-Scanned: amavisd-new at informatik.uni-bremen.de
Received: from submithost.informatik.uni-bremen.de (submithost2.informatik.uni-bremen.de [134.102.200.7]) by mailhost.informatik.uni-bremen.de (8.14.5/8.14.5) with ESMTP id wA9N0RaL019573; Sat, 10 Nov 2018 00:00:32 +0100 (CET)
Received: from [IPv6:2001:67c:1232:144:4ca7:1ca5:121e:cc52] (unknown [IPv6:2001:67c:1232:144:4ca7:1ca5:121e:cc52]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by submithost.informatik.uni-bremen.de (Postfix) with ESMTPSA id 42sFx45Ny3z1Bqk; Sat, 10 Nov 2018 00:00:24 +0100 (CET)
Content-Type: text/plain; charset=utf-8
Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\))
From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <6DAEE31A-A9D1-4F58-A9AE-DE9005809E36@gmail.com>
Date: Sat, 10 Nov 2018 06:00:20 +0700
Cc: =?utf-8?Q?Ari_Ker=C3=A4nen?= <ari.keranen@ericsson.com>, =?utf-8?Q?Christian_Ams=C3=BCss?= <christian@amsuess.com>, "fluffy@cisco.com" <fluffy@cisco.com>, Shantanoo Desai <des@biba.uni-bremen.de>, "core@ietf.org" <core@ietf.org>
X-Mao-Original-Outgoing-Id: 563497218.604251-649c48453ad560c49bd7ef69804476b4
Content-Transfer-Encoding: quoted-printable
Message-Id: <7B224439-4DFD-4774-9FDA-E92112A31A11@tzi.org>
References: <3643AE5F1967B74C86F1D72E6EB108926367EB@EXCH1.biba.uni-bremen.de> <9315AE8F-0893-4587-8FF3-8EA43BF48D64@gmail.com> <20181108071803.GA4264@hephaistos.amsuess.com> <993797F0-02BB-46C0-94C2-FD62C311635D@gmail.com> <20181108183715.GB26534@hephaistos.amsuess.com> <HE1PR07MB4236DFCE18F76CB730476DEB85C60@HE1PR07MB4236.eurprd07.prod.outlook.com> <6DAEE31A-A9D1-4F58-A9AE-DE9005809E36@gmail.com>
To: Michael Koster <michaeljohnkoster@gmail.com>
X-Mailer: Apple Mail (2.3445.9.1)
Archived-At: <https://mailarchive.ietf.org/arch/msg/core/Rbm9E7Ff_M6uqHpButVfbSIV4gk>
Subject: Re: [core] [SenML] Multiple values in a measurement
X-BeenThere: core@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Constrained RESTful Environments \(CoRE\) Working Group list" <core.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/core>, <mailto:core-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/core/>
List-Post: <mailto:core@ietf.org>
List-Help: <mailto:core-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/core>, <mailto:core-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 09 Nov 2018 23:00:45 -0000

On Nov 9, 2018, at 21:46, Michael Koster <michaeljohnkoster@gmail.com> wrote:
> 
> Also, Is the example in the RFC wrong? This doesn't resolve to a globally unique identifier 
> 
>    [
>      {"bn":"2001:db8::2/","bt":1.320078429e+09,
>       "n":"temperature","u":"Cel","v":25.2},
>      {"n":"humidity","u":"%RH","v":30},
>      {"bn":"2001:db8::1/","n":"temperature","u":"Cel","v":12.3},
>      {"n":"humidity","u":"%RH","v":67}
>    ]

In RFCs, 2001:db8::x is code for “an IP address".  That is “globally unique” (unless RFC 1918, which we don’t have in IPv6).  Obviously its ownership can change over time.  But that is then disambiguated by bt/t.

> To summarize, it seems overly restrictive to the general use of senml to require that each senml pack be identified with a globally unique resource. (please correct me if I mis-stated this)

This is a choice that we did debate a lot.  The RFC documents the outcome of that debate.  The other choice would have been valid as well.

(My personal view is that an RFC 6919 “MUST (BUT WE KNOW YOU WON’T)” would have been closer to what we’ll find in real world use of SenML.  But at least we gave an incentive to other SDOs to look for ways to obtain unique identifiers.)

Grüße, Carsten