[occi-wg] OCCI Categories and Types

[Alexander Papaspyrou]

Ralf,

Am 13.08.2010 um 11:59 schrieb Ralf Lyren:

> Each category, defined by schema + term, can have a set of associated  
> attributes. What namespace restrictions/rules are imposed on these  
> attributes?
> Currently Core&Models says provider defined categories must be in a  
> different namespace but no more. Maybe extend this a bit further as to  
> avoid namespace conflicts while combining many categories? I believe  
> earlier revs of the spec said something like:
> com.example.<category_term>.<attr_name>

I don't recall that this ever has been discussed, but it certainly is a very good idea.

> I do not quite understand the various Content-type headers used in the  
> examples. Are they of any significance to the definition/use of categories?

No. They are just supposed to make it easier to spot the type within the core model. So, the MIME types would be something like

application/occi-resource (for the Resource class from core)
application/occi-link (for the Link class from core)
... (whatever else is defined as a class in core)

That way, you don't have to analyze the details of a REST resource, but just look at the MIME type delivered by the OCCI container.

> And just a few notes on the examples, sorry if it sounds picky but  
> consistency really helps understanding:
> 
> - Category: compute; scheme="http://prov.com/occi#";
>   Scheme should be "http://prov.com/occi/resource#" right?

The URIs we used just served as example. For a category with term "foo" and scheme "bar", you would have

Category: foo; scheme="bar";

> - Link: </compute/123-123-123;start>; type="application/occi-action";
>   Is the "type" attribute of the Link header something new? If so, how it  
> is defined?

We have been discussing yesterday whether the type attribute is necessary at all. Probably this has not found its way into the Wiki.

> - In Link header: rel="category http://prov.com/occi#action"
>   Is the format rel="category XXX" something new as well?

Yes. We tried to stick as much as possible to the IETF nottingham Link draft [1], not adding any additional vendor-specific extensions.

HTH.

Best,
Alexander

[1] http://tools.ietf.org/html/draft-nottingham-http-link-header-04

> On Fri, 13 Aug 2010 11:10:18 +0200, Edmonds, AndrewX  
> <andrewx.edmonds at intel.com> wrote:
> 
>> Hi all,
>> Yesterday Alexander and I spent some time exploring and discussing OCCI  
>> categories. These categories make up the type system for OCCI and I've  
>> documented our discussion here [1]. We'd love to hear feedback, comments  
>> etc!
>> 
>> Andy
>> 
>> [1]  
>> http://forge.gridforum.org/sf/wiki/do/viewPage/projects.occi-wg/wiki/Category
>> 
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-- 
Alexander Papaspyrou
alexander.papaspyrou at tu-dortmund.de

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