Re: Requesting the RDF MIME type of an image

Hi Dan,


On 22 Oct 2009, at 22:52, Dan Smith wrote:

> Hello there,
>
> I'm researching into the semantic analysis of complementary  
> resources right now, and I'm about to start work on an automated  
> image annotator.
>
> I have got to the stage of my RDF file being generated and I'm now  
> trying to figure out a way for the user or their application to  
> retrieve the RDF version of the image.
>
> I have found a couple of helpful things from [ http://www.w3.org/TR/photo-rdf/ 
>  ];
>
> "The RDF can be also be fetched directly without doing Content  
> Negotiation, by just adding the wanted MIME type after a semicoln  
> (;) e.g.: foo.jpg;application%2Frdf+xml ("%2F" is "/", escaped for  
> occurrence in a URL.)"
>
> This doesn't work for me on the image set [ http://jigsaw.w3.org/Yves/Australia/1998/04/ 
>  ] which are supposed to support RDF metadata.

Sure, I think this site is rather old now, and it seems like the curl  
calls to retrieve RDF don't work as expected, as you seem to have  
noticed. For sanity purposes, I to was not able to extract the rdf  
from the sample image URIs linked to from the /photo-rdf page.

The common way to perform this content-negotitation is detailed here :

http://www.w3.org/TR/swbp-vocab-pub/

The photo-rdf page you had a look at on the W3C page is just a "Note",  
and far from perfect, e.g.  the MIME type for RDF is presented as  
application/rdf on the page.

The way I would do it is as follows:

Have a URL like below : which is for the image in question.

http://foo.com/pictures/1214123412

Which you can perform content negotiation on, so that if you :

request "Accept:application/rdf+xml" you would get back RDF

and if you request html you would get back an HTML doc, perhaps an  
html page with the image, and a human readable representation of all  
of the metadata.

and if you request image/jpeg (or whatever the correct MIME type is  
for a .jpg file) you would get back the Image itself.

This would allow you to change the file format of your picture if ever  
need be (i.e. from .jpg to .png for example), keeping the URI of the  
image constant and neutral to file format.

>
> I also saw somewhere that you can actually embed the RDF data inside  
> a COM comment in the image too.

Regarding the embedded RDF in pictures, I think you are talking about  
Adobe's XMP (Extensible Metadata Platform) :

http://www.adobe.com/products/xmp/

This allows one to write RDF into the header of a JPEG. I think this  
is touched upon in the W3C photo-rdf page you mailed round.

As for image RDF stuff, this page is a nice place to start:

http://www.kanzaki.com/works/2004/imgdsc/0106.html

I hope this helps,

Mischa

> *** There's not much else to dig around in on this topic by the  
> looks of things, could anyone give me a pointer?
>
> Many thanks,
> Dan Smith

_________________________________
Mischa Tuffield
Email: mischa.tuffield@garlik.com
Work: http://www.garlik.com/
Homepage: http://mmt.me.uk/
FOAF: http://mmt.me.uk/foaf.rdf#mischa