Re: [core] Questions & Comments for PubSub updated Proposal
Jim Schaad <ietf@augustcellars.com> Fri, 02 August 2019 15:48 UTC
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From: Jim Schaad <ietf@augustcellars.com>
To: 'Christian Amsüss' <christian@amsuess.com>
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Date: Fri, 02 Aug 2019 08:48:26 -0700
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Subject: Re: [core] Questions & Comments for PubSub updated Proposal
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-----Original Message----- From: Christian Amsüss <christian@amsuess.com> Sent: Thursday, August 1, 2019 1:46 AM To: Jim Schaad <ietf@augustcellars.com> Cc: core@ietf.org Subject: Re: [core] Questions & Comments for PubSub updated Proposal Hello Jim, hello pubsub authors, my personal take on this: I think that most those points can addressed by a variation on the proposal that has been floating but not made its way into the text yet: Rather than all attributes being attached to the topic, some are on the data resource. Compare the following to item 3.5: Request: GET </ps/topics/1234> Response: 2.05 Content Content-Format: CoRAL rdf:type <http://example.org/pubsub/topic> has-published-item true publish -> </ps/data/1234> [ method 3 ] created dt'2019-07-08T15:35:00+0200' last-modified dt'2019-07-08T15:35:00+0200' owner <http://ericsson.example/people/ari> max-rate 50 expires dt'2019-07-15T15:35:00+0200' topic-data </ps/data/1234> { unit "Cel" rt "oic.r.temperature" # that was "topic-title" on the topic in proposal.txt title "My Office Room Temperature" # that was "publisher" on the topic in proposal.txt owner <http://ericcson.example/people/klaus> building 18 floor 1 } We'd still need to, for all the properties involved, decide which terms to use and where to attach them, but it completely sidesteps the topic of inheritance (which would indeed be tricky -- the resource type of a control resource is "pubsub topic control resource", if it's a oic.r.temperature at the same time, that's ... odd). A good criterion for whether something is an attribute of the control or the data resource is the question "Does it matter whether this is used in a pubsub context?": If it is, it should be on the control resource, otherwise it's on the data resource. [JLS] Yes - That is very similar to the way that was thinking. I had not gone as far as renaming some of the fields so that there is more consistency but that makes things even better. There is the interesting question of what the target is for a creation post, a patch would use the correct target, but I think that this could be done as [ path.type: relative-path] which is the closest that I can see to being the equivalent of "." which would make sense. This does still not quite answer this: > 2. It is not clear to me if a data node is supposed to be able to > provide a CoRAL document for information that relates to it. If someone only knows the data resource, there's no way back from there to the control resource, and no way to get its metadata (that'd be a PROPFIND-style operation probably, and I don't think we want that). There are still CoRAL statements about the topic, but the easiest way to obtain them is to look into the control resource's CoRAL document that describes the topic as well as above. (Which is also how they could be updated, by PATCHing that resource once a patch format for CoRAL is there, or by PUTting back a modified representation, where the server would reject changes it can't do, like the created date or the topic-data URI). [JLS] Right - somebody who know both that this was a pub-sub server and understood CoRAL could do this with REQUEST FETCH </ps/topics> rdf:type <http://example.org/pubsub/topic> topic-data </ps/data/1234> This would find and return the information about the topic based on the topic-data path. If you just do link format then you are out of luck. Jim Best regards Christian -- To use raw power is to make yourself infinitely vulnerable to greater powers. -- Bene Gesserit axiom
- [core] Questions & Comments for PubSub updated Pr… Jim Schaad
- Re: [core] Questions & Comments for PubSub update… Christian Amsüss
- Re: [core] Questions & Comments for PubSub update… Jim Schaad