Re: [Uri-review] Request review for URI schemes for CoAP over reliable transports
Graham Klyne <gk@ninebynine.org> Wed, 17 May 2017 16:50 UTC
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Date: Wed, 17 May 2017 17:43:40 +0100
From: Graham Klyne <gk@ninebynine.org>
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Subject: Re: [Uri-review] Request review for URI schemes for CoAP over reliable transports
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Carsten, all, First, my apologies for the very delayed response. (I've (a) had some email problems which meant I couldn't post to this list, and (b) been travelling with very limited Internet access.) So I've only just reinstated my access to post to this list. So, hoping it's not *too* late to chip in... I am concerned that these scheme registrations (with multiple schemes for the same resource accessed using a different protocol) present an "antipattern" that was controversial when a similar proposal was raised about 18 months ago; e.g. see an earlier thread [1] about the "rr+*" URI proposal, and in particular the response from Roy Fielding [2], specifically this: [[ A URI scheme should define what it names and how that naming maps to the URI syntax. There is nothing wrong with using separate schemes for different transports if those transports are essential parts of the name (e.g., if something named Fred at TCP:80 is different from something named Fred at UDP:89898). [...] In short, I think you need to better document what each URI scheme means from the perspective of a server and then what the client is expected to do with such a URI. ]] [1] https://mailarchive.ietf.org/arch/search/?email_list=uri-review&gbt=1&index=ZXTfNQ7PDxHBSccrqrrbGH5N-Ko [2] https://mailarchive.ietf.org/arch/msg/uri-review/ZXTfNQ7PDxHBSccrqrrbGH5N-Ko I can see no difference between a CoAP resource referenced using the different URI schemes defined in the draft, and as such it appears to be an abuse of the URI framework, a principle of which is that multiple URIs for identifying the same resources should be avoided where possible [3]. Part of the role of URIs as identifiers is that they hide rather than expose the purely technical mechanisms used when accessing a resource. (Where a technical mechanism is exposed, as in "http:", it is as part of the identifying mechanism. [3] http://www.w3.org/TR/webarch/#uri-aliases How is this use of CoAP expected to sit within the wider framework of the World Wide Web (for which URIs are a core specification). If you're just using these strings to select different transports, why do they need to be URIs at all? #g -- On 21/04/2017 06:32, Carsten Bormann wrote: > It seems we never formally requested a review of the four new URI schemes for CoAP over TCP, TLS, and WebSockets, as requested in > > https://tools.ietf.org/html/draft-ietf-core-coap-tcp-tls-07#section-10.5 > > To summarize these four schemes: > > coap-tcp-URI = "coap+tcp:" "//" host [ ":" port ] > path-abempty [ "?" query ] [ "#" fragment ] > > coaps-tcp-URI = "coaps+tcp:" "//" host [ ":" port ] > path-abempty [ "?" query ] [ "#" fragment ] > > coap-ws-URI = "coap+ws:" "//" host [ ":" port ] > path-abempty [ "?" query ] [ "#" fragment ] > > coaps-ws-URI = "coaps+ws:" "//" host [ ":" port ] > path-abempty [ "?" query ] [ "#" fragment ] > > For the details, please see the draft, which has completed IETF last call. > (These are patterned after “coap:” and “coaps:” in RFC 7252, which are defined over UDP and DTLS, respectively.) > > Grüße, Carsten > > _______________________________________________ > Uri-review mailing list > Uri-review@ietf.org > https://www.ietf.org/mailman/listinfo/uri-review >
- [Uri-review] Request review for URI schemes for C… Carsten Bormann
- Re: [Uri-review] Request review for URI schemes f… Graham Klyne