[core] Review of draft-ietf-core-coap-pubsub-06

[Jim Schaad <[e-mail]>]

Here is a more detailed review of this document:

1.  Section 2 - You should update the keywords with text from RFC 8174

2.  Section 2 - I am not sure that I would agree that a top corresponds to a
valid CoAP URI.  I believe that this is really a CoAP URI-Path as the same
topic could appear on different brokers or under different schemes.   The
scheme/URI-host would appear to be the broker and not the topic.  This is
re-enforced by the topic in section 3.4

3. Section 3.5 - I think that the brokerless in the title should be
capitalized.

4. Section 3.5 - I understand the use case for having a broker version of
this protocol.  I am not clear why the brokerless version is useful.  It
might be a good idea to include a description of where this would be used as
opposed to normal CoAP functionality.

5.  Section 4.1 - Should there be a resource type of 'core.ps.topic' to
distinguish between resources which are supported by the server directly and
those which are pub/sub topics.  This would complete the 'core.ps',
'core.ps.discover' set of resource types.  Specifically I am trying to map
the different operations to the different resource types.

6. Section 4.1 - The definition of 'ps' implies that topics can be rooted at
/ rather than at /ps.  While I don't have a problem with this I think that
by saying that it 'ps' is optional seems to be slightly odd.  It would make
more sense to me to say that '{ps}' is not optional but can be the
equivalent of '/.' The assumption in this case is that what would be
returned by .w-k/core would be '</>;rt=core.ps;ct=40' rather than '<>' as
the refpath.  

7. Section 4.1 - I am not completely clear on this.  Is DISCOVERY only
supported by rt=coap.ps.discovery or is it also supported by rt=coap.ps?  

8. Section 4.1 - Is discovery only permitted to find those resources which
are subordinate to it for rt=coap.ps.discovery or can it search all topics
published in the PS?

9.  Section 4.1 - Is there a policy of some type about what topics are and
are not visible under .w-k/core?  I was planning to hide all of them and
only expose them via the /ps resource.  This seems to be contra-indicated by
the example in figure 5 but is similar to what happens in RD.

10.  Section 4.2/3  You should think about what happens if I use a multipart
content for publishing.  This would allow for publishing multiple content
types at the same time which might be an interesting feature.  This allows
for multiple content types w/o the broker having to do the content
conversions.

11. Section 4.3 - Am I correct in assuming that max-age defaults to 60
seconds for a publish operation?  There is a different default value
specified for CREATE but not here.  Another possible default value would
have been the topic lifetime.

12. Section 5 - I think you need to re-write the text dealing with con as
this does not appear to be in the RD any more.

Jim