Re: [oslc-core] Choice for Configuration context request headder (was: [oslc-core] Agenda for 15 May 2014)

[John Arwe <johnarwe@us.ibm.com>]

From Ian> Vary: Link
...But this has a broader scope since
Link values have meaning outside of CM.  I think has some bearing
on the decision on whether or not to use Link or mint a fresh header.

This is true; even in httpbis, Vary is a blunt tool.

The best "counter" I have for this point is that (today) Link is primarily used as a *response* header, whereas Vary-identified headers are tests on the *request* message.  

Technically Link headers are allowed on requests (it takes careful reading of 5988 to even see this), but the only actual usage of this that I'm aware of is in LDP on create (which would not be cacheable responses anyway).

So in near-term practical usage, unlikely to be an issue.  Longer term - which we do have to consider - it's more of a judgement call.  If someone comes up with a request-message Link header that goes viral tomorrow, then the Vary behavior effectively would mean that the config requests were uncacheable by generic caches.  If we were implementing our own caches, of course they could choose to have a deeper understanding of the messages involved.

Best Regards, John

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