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Re: Using MIME types in RDF/DAML and Image Metadata

From: Yarden Katz <katz@underlevel.net>
Date: Sun, 30 Mar 2003 19:12:20 -0500
To: Dave Beckett <dave.beckett@bristol.ac.uk>
Cc: www-rdf-interest@w3.org
Message-ID: <86he9ks8bf.fsf@underlevel.net>

Dave Beckett <dave.beckett@bristol.ac.uk> writes:

>>>>Yarden Katz said:
>
> [Aside, this message probably didn't need cross posting ]

Sorry, my bad, I meant to post only to www-rdf-interest.

>> Hi,
>> 
>>   What are some approaches to assign MIME-types to certain RDF or DAML
>>   resources?  For example, consider the following:
>> 
>>     <daml:ObjectProperty rdf:ID="Picture">
>>       <rdfs:label>A Picture</rdfs:label>
>>       <rdfs:comment>A cute picture class in DAML</rdfs:comment>
>>       <rdfs:domain rdf:resource="#SomeObject"/>
>>       <rdfs:range rdf:resource="#????"/>
>>     </daml:ObjectProperty>
>
> I'm not familiar with the semantics of daml:ObjectProperty (or the
> OWL equivalent), however ...
>
>>   An agent attempting to render RDF data has no way of knowing that
>>   resources linked to using the above property are images and are to
>>   be handled as such.  How can these meaning be conveyed in RDF?  The
>>   obvious method seems to be to assign a MIME type such as
>>   "image/jpeg" as the range of this property, but I do not know how
>>   that can be expressed.  Googling showed up a seemingly relevant link
>>   "Mapping Between Content-Types (MIME types) and URIs" from
>>   <http://rdfig.xmlhack.com/2001/05/09/2001-05-09.html> but it is
>>   broken.  Any ideas you may have on how to attach this elementary
>>   problem would be great, whether involving usage of MIME or not.
>
> A quick google finds:
>
>   Mapping between URIs and Internet Media Types
>   TAG Finding 8 April 2002 (Revised 27 May 2002)
>
>   http://www.w3.org/2001/tag/2002/01-uriMediaType-9

As I pointed out in my original post:

 Googling showed up a seemingly relevant link
 "Mapping Between Content-Types (MIME types) and URIs"

The W3C document you made reference to contains two broken links to
IETF documents, one of which I mentioned above.

> The other way uses familiar and well deployed Dublin Core vocabulary
> an it's dc:format property.  It takes as primary recommend value the
> IMT / MIME Type as a literal.  You might be able to do some inference
> magic to imply that all your 'Picture's have the dc:format
> "image/jpeg".  Otherwise you'd need to put it in the instance data.

Great!  I never knew about this property of DC.  However, I'm not
quite sure I understand your suggestion about inferencing.  As far as
I can tell, I could use dc:format as follows:

  Given: <Picture rdf:resource="http://foo/bar.jpg">

  <rdf:Description rdf:resource="http://foo/bar.jpg">
    <dc:format>image/jpeg</dc:format>
  </rdf:Description>

But I'm unsure of a way to express that "all resources pointed to by
[i.e., everything in the rdfs:range] 'Picture' have dc:format of
image/jpeg".  If I hardcode it into the agent, well, then it's not
really inferencing :)

> See http://dublincore.org/documents/1999/07/02/dces/
> and many DC and RDF apps use this already.
>
>> 
>>   I have a second question that's related to the above: is there some
>>   uniform way to note coordinates on an image (similar to an image
>>   map) in RDF?  For example, expressing something a long the lines of
>>   "Instances of Object X should be placed in coordinate (X, Y)"  The
>>   most relevant link I found was:
>>   <http://www.w3.org/2001/08/rdfweb/foafwho/imagemap/> but it does not
>>   show an RDF representation of an image map, only the plain HTML one.
>
> Sorry, I've no info on this question.
>
> Dave

Thanks,
-- 
Yarden Katz <katz@underlevel.net>  |  Mind the gap
Received on Sunday, 30 March 2003 18:40:45 GMT

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