W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2003

Re: RDF query and Rules - my two cents

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 20 Nov 2003 15:41:50 +0200
Cc: <www-rdf-interest-request@w3.org>, "Graham Klyne" <GK@ninebynine.org>, "Jim Hendler" <hendler@cs.umd.edu>, "Dan Brickley" <danbri@w3.org>, <www-rdf-rules@w3.org>, <www-rdf-interest@w3.org>
To: "ext Danny Ayers" <danny666@virgilio.it>
Message-Id: <4B31B186-1B5F-11D8-8364-000A95EAFCEA@nokia.com>


On Thursday, Nov 20, 2003, at 13:52 Europe/Helsinki, ext Danny Ayers 
wrote:

>
>
>>> I haven't fully digested your arguments yet, but would be grateful if
>>> you
>>> could answer one quick question: can't the functionality of MGET be
>>> achieved
>>> just using mimetypes?
>>>
>>
>> No. Tried that. It doesn't work. Because you can't differentiate
>> between request for a description of a resource, versus a request
>> for a representation of a resource that happens to be a description
>> of another resource.
>
> request for a description of a resource:
>
> http://example.org/xxx [mimetype:application/rdf+xml-description]
>
> request for a representation of a resource
>
> http://example.org/xxx [mimetype:application/rdf+xml]
>
> The first of these corresponds to MGET, the second to GET. Rather than 
> the
> switch being on the verb, it's on the mimetype. If the latter 
> representation
> happens to be a description of another resource, how is that 
> significant?
> What is the logical difference between these approaches?

Well, what happens when that description is available in RDF/XML,
N3, N-Triples, XTM, HTML, etc.???

Do we have a parallel set of mime types, such that for any mime type
x/y we have x/y-description?

Or do we just forbid any other encoding than RDF/XML?

I don't find either option the least bit appealing.

It's really just a variant of the URI-suffix approach. E.g. append
_META or such to the end of any URI to get the URI that denotes its
metadata description.

>
>> Or if the resource in question has an RDF/XML representation, you
>> can't use content negotiation to ask for a description in RDF/XML
>> because how then do you differentiate between the RDF/XML 
>> representation
>> and the RDF/XML description.
>
> Different mime type, recognized at both ends. A request for
> "application/rdf+xml-description" means "please return a concise 
> bounded
> description of the resource denoted by the request URI", the correct
> behaviour of the server is confirmed by the returned Content-Type.
>
>> I even tried defining a distinct MIME type for concise bounded
>> descriptions, but as I indicate above, in the case where you want
>> a description of a description, it doesn't work
>
> I'd be grateful for an example of how this is different with MGET, it 
> sounds
> like there's something I'm not grokking here.
>

See above. I.e. a description can have multiple representations...

>> In short, there are certain "meta" distinctions which the SW needs
>> that simply must be kept distinct from the existing web semantics.
>> The distinction between requests involving a representation (web)
>> and requests involving a description (sw) is one such distinction.
>
> Yes, I think you've made a good case for the distinction, but I don't 
> see
> why this distinction couldn't be made through mime type negotiation 
> (or some
> other existing mechanism)...
>
>> And IMO the cleanest way to implement that is with distinct methods
>> such as MGET, MPUT, and MDELETE.
>
> Still not convinced... ;-)
>

Maybe the above comments, then, were useful to that end.

Cheers,

Patrick


> Cheers,
> Danny.
>
Received on Thursday, 20 November 2003 08:44:09 GMT

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