This was mentioned on the call today (during which I was unable to speak despite calling in twice - presumably something at my end) and I definitely agree with Alexis in that we shouldn't create new technology where we don't absolutely have to. I wrote the Web Categories Internet-Draft for OCCI because there didn't appear to be any existing mechanism for this, but eventually came to the realisation (like you) that it would be possible to convey this information via the Link: header. What's possible and what's sensible aren't always the same thing though and I'd argue that there's not much difference in terms of handling effort as you'll most likely be dealing with raw headers anyway (remember we need schemes so even if there was some intelligence to the handling of links we'd have to bypass it for this).

A greater concern for me is the handling of properties/attributes. Rather than give people carte blanche in terms of encouraging them to mint their own headers for each additional property, I think it makes a lot more sense to have e.g. a "Property" header which acts like a kind of server-side cookie (and is modelled after Set-Cookie[2]). This is what is currently documented and all the examples I've thrown at it all work nicely thus far.

Sam

On Sat, Jan 16, 2010 at 8:53 AM, Mike Kelly <mike@mykanjo.co.uk> wrote:

Hi Sam,

A reason for sticking to Link headers could be to keep 'consistency' in the protocol's hypertext mechanisms? Another reason is that tools for handling Link headers, client and server side, are likely to have broader availability.
Cheers,
Mike

Sam Johnston wrote:

Mike,

Thanks for taking the time to look at our specifications. The categories are dealt with in a separate IETF Internet-Draft (http://tools.ietf.org/html/draft-johnston-http-category-header-00) but it's true that they could be layered on top of the Link: header. I hadn't considered this option at the time but it does make some sense. OTOH we need to sensibly layer properties/attributes on top of HTTP headers so we'll probably be blazing our own trail there anyway (using Property:/Attribute: headers modelled after Set-Cookie[2]:).

Sam

On Fri, Jan 8, 2010 at 8:23 PM, Mike Kelly <mike@mykanjo.co.uk <mailto:mike@mykanjo.co.uk>> wrote:

I really like the protocol, you've done a great job

I have a question: Why is Category given a unique header, and not
simply
treated as another type of link relation for a resource?

i.e.

Category: compute;
scheme="http://purl.org/occi/kind/";
label="Compute Resource"

.. could that actually be written as:

Link: <http://occi.org/kinds/compute>;
rel=<http://purl.org/occi/kind>;
title="Compute Resource"

Cheers,
Mike
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