Re: [core] AD review of draft-ietf-core-senml-12
Ari Keränen <ari.keranen@ericsson.com> Thu, 01 March 2018 06:41 UTC
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From: Ari Keränen <ari.keranen@ericsson.com>
To: Alexey Melnikov <alexey.melnikov@isode.com>
CC: Cullen Jennings <fluffy@cisco.com>, Carsten Bormann <cabo@tzi.org>, "core@ietf.org WG" <core@ietf.org>
Thread-Topic: [core] AD review of draft-ietf-core-senml-12
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Date: Thu, 01 Mar 2018 06:41:02 +0000
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Subject: Re: [core] AD review of draft-ietf-core-senml-12
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Hi Alexey, Thank you for the review! And sorry for the late reply. We have now addressed all your comments in the PR 98: https://github.com/core-wg/senml-spec/pull/98 Also see answers to your comments inline. Cheers, Ari > On 11 Jan 2018, at 23.12, Alexey Melnikov <alexey.melnikov@isode.com> wrote: > > Hi, > I nearly finished my review (I still need to double check a few things > on fragment identifiers and media type registration compatibility with > base media types like application/xml). I think the document is > generally in a good shape, but there are a few things that we need to be > fixed or discussed first. > > I will also ask for a couple of extra reviews of this document. > > Major: > > 1) In order to be able to register application/senml+exi and > application/sensml+exi, +exi suffix needs to be registered (+json, +xml > and +cbor are already registered. See > <https://www.iana.org/assignments/media-type-structured-suffix/media-type-structured-suffix.xhtml#structured-syntax-suffix>). > There is separate registration procedure for this. Note that there was > already a discussion about registering +exi and a Designated Expert > opinion was that EXI is not a generic encoding format (JSON, CBOR and > XML are) that can be decoded without knowing schemaID. The WG can argue > against this point, but I am not convinced that the WG will convince the > Designated Expert otherwise. > > If you don't want to register the +exi suffix, the easiest fix to the > document is to change "+" in application/senml+exi and > application/sensml+exi to "-", as "-" doesn't have special semantics > associated with suffixes. Fixed by changing to "-exi" as you suggested and was discussed in this thread already. > > 2) The following omissions are pretty easy to fix, but I think they are > important enough for readers of documents: > > First references to UTF-8, XML, Relax NG, XML Schema need Normative > References. (Some of these are missing Normative References, some of > these are just missing them on first use.) Added references for each. > I also suspect that some IESG members will have an opinion that the CDDL > reference is Normative. So you might need to choose between making CDDL > reference Normative (which will result in this document not being > published until CDDL draft is also approved for publication) and > removing CDDL definition from the document. Clarified that this is informative (similar text was OK with earlier RFC): As a convenient reference, the JSON and CBOR representations can be described with the common CDDL [I-D.ietf-cbor-cddl] specification in Figure 1 (informative). > Minor: > > > Section 2: > > Some devices have accurate time while others do not so SenML supports > absolute and relative times. Time is represented in floating point > as seconds and values greater than zero represent an absolute time > relative to the Unix epoch while values of 0 or less represent a > > Does Unix epoch need a reference? Added reference to the POSIX spec and added new clarifying text: Time is represented in floating point as seconds. Values greater than zero represent an absolute time relative to the Unix epoch (1970-01-01T00:00Z in UTC time) and the time is counted same way as the Portable Operating System Interface (POSIX) "seconds since the epoch" [TIME_T]. Values of 0 or less represent a relative time in the past from the current time. > relative time in the past from the current time. > > 3. Terminology > > The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", > "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and > "OPTIONAL" in this document are to be interpreted as described in > [RFC2119]. > > I suggest you switch to the updated phrasing that allows for lowercase > "must", etc: > > The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", > "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and > "OPTIONAL" in this document are to be interpreted as described in > BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all > capitals, as shown here. Fixed as suggested. > In 4.4 > > Although it is RECOMMENDED that concatenated names are represented as > URIs [RFC3986] or URNs [RFC8141], the restricted character set > specified above puts strict limits on the URI schemes and URN > namespaces that can be used. > > I understand that this phrasing is a result of discussions in the WG. Is > it possible/useful to point out some typical URI schemes that can't be > used here, such as HTTP/HTTPS/COAP? Added two examples: However, the restricted character set does not allow the use of many URI schemes, such as the 'tag' scheme [RFC4151] and the 'ni' scheme [RFC6920], in names as such. > In Section 5: > > The mantissa SHOULD > be less than 19 characters long and the exponent SHOULD be less than > 5 characters long. > > The above two SHOULDs: is the above sufficient for interoperability? > What would happen if the SHOULD is not followed? The SHOULDs are there to facilitate efficient parsing of the data. We added this: In the interest of avoiding unnecessary verbosity and speeding up processing, the mantissa SHOULD be less than 19 characters long and the exponent SHOULD be less than 5 characters long. > In 5.1.2: > > SenML defines a > separate media type to indicate Sensor Streaming Measurement Lists > (SensML) for this usage (see Section 12.3.2). > > It would be good to mention something about this in the IANA > registrations for media types, as on a cursory look one can think that > there are lots of duplicated registrations. Added to 12.3 (Media Type Registrations): This document registers media types for each serialization format of SenML (JSON, CBOR, and EXI) and also media types for the same formats of the streaming use (SensML). > I just want to double check regarding binary data in XML. I assume there > is a need to use XML escaping for bytes not otherwise allowed in XML? It > might be worth pointing this out to avoid naive (and buggy) implementations. Base64 encoding is used with binary data: https://tools.ietf.org/html/draft-ietf-core-senml-12#section-7 > The following comment applies to all media type registrations: > > 12.3.1. senml+json Media Type Registration > > Interoperability considerations: Applications should ignore any JSON > key value pairs that they do not understand. This allows backwards > compatibility extensions to this specification. The "bver" field can > be used to ensure the receiver supports a minimal level of > functionality needed by the creator of the JSON object. > > Is it worth mentioning here special treatment of keys that end with "_": > > Implementations MUST ignore fields they don't recognize unless that > field has a label name that ends with the '_' character in which > case an error MUST be generated. > > (The above text is from page 7. Might need to reword it in the media > type registration template)? Changed this to: Interoperability considerations: Applications MUST ignore any JSON key value pairs that they do not understand unless the key ends with the '_' character in which case an error MUST be generated. This allows backwards compatible extensions to this specification. And similar changes to all other registrations. > In Section 13: > > You should also mention that defined formats don't include executable > content. (Media Type reviewers typically ask this question) Added to Section 13: The SenML formats defined by this specification do not contain any executable content. However, future extensions could potentially embed application specific executable content in the data. > Nits: > > Abstract > > This specification defines media types for representing simple sensor > measurements and device parameters in the Sensor Measurement Lists > (SenML). Representations are defined in JavaScript Object Notation > (JSON), Concise Binary Object Representation (CBOR), eXtensible > Markup Language (XML), and Efficient XML Interchange (EXI), which > share the common SenML data model. A simple sensor, such as a > temperature sensor, could use this media type in protocols such as > > this media type --> one of these media types Fixed. > HTTP or CoAP to transport the measurements of the sensor or to be > configured. > > > First references to HTTP, COAP, S/MIME and TLS need Informative References. Fixed. > 12.1. Units Registry > > IANA will create a registry of SenML unit symbols. The primary > purpose of this registry is to make sure that symbols uniquely map to > give type of measurement. > > give --> given Fixed. > Best Regards, > Alexey > > > _______________________________________________ > core mailing list > core@ietf.org > https://www.ietf.org/mailman/listinfo/core
- [core] AD review of draft-ietf-core-senml-12 Alexey Melnikov
- Re: [core] AD review of draft-ietf-core-senml-12 Olaf Bergmann
- Re: [core] AD review of draft-ietf-core-senml-12 Ari Keränen