Re: Issue-80: Post media types usable for Create; background for proposal

Related-but-distinct point #1: Creates can be done via means other that 
POST.  Both PUT and PATCH allow creates explicitly; we discourage PATCH as 
create IIRC, but we're more neutral on PUT in part due to discussions at 
F2F1.

When I made the proposal for a new header scoped specifically to 
POST-for-create, I did that intentionally.  The HTTP-defined semantics of 
PUT and PATCH are more constrained than POST; I think in both cases the 
worst-case "penalty" a client intending a create-only pays is making a 
prospective HEAD request on the "new resource"'s URI; if it receives a 
404, the semantics it should anticipate are clear (create) although this 
is never guaranteed due to race conditions.  Simpler still is to make the 
request conditional (If-None-Match: *).

Thus, I don't see any need to add to "what is" for create via PUT/PATCH. 
HTTP as it is appears to be sufficient.  This might be worth pointing out 
in Deployment.



Related-but-distinct point #2: looking across the Methods that LDP uses, 
how does a client know which media types are supported?

For responses, HTTP Accept should suffice.  Knowledge that the client is 
interacting with an LDP Server constrains that a bit further (MUST offer 
Turtle for LDPRs, etc).

For requests, we have (by method)
a.      HEAD: n/a (no request/response payload)
b.      POST: Accept-Post-Create proposal in issue-80 covers LDP’s needs
c.      GET: n/a (no request payload)
d.      PUT: rely on conneg; nothing prospective; most servers will 
probably accept "any" format they serve
e.      PATCH: Accept- Patch already covers the need

I realize there are edge cases (PUT back updated HTML for an LDPR may be 
non-sensical unless it's "special" HTML with RDFa/etc), this is just the 
broad-brush version to see if it prompts any needed discussion.  Unless we 
feel a need for an "Accept-Put" analog ... and I don't think LDP is 
intentionally trying to encourage PUTs that much... that state might be 
fine.


Best Regards, John

Voice US 845-435-9470  BluePages
Tivoli OSLC Lead - Show me the Scenario