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Re: [Image] How to identify images in an RDF context

From: Jerome Euzenat <Jerome.Euzenat@inrialpes.fr>
Date: Thu, 10 Feb 2005 11:44:50 +0100
Message-Id: <a06001a04be30e6cae380@[]>
To: Karl Dubost <karl@w3.org>, semantic-web@w3.org

Hello Karl,

	very interesing questions. A starting point for a modelling course.

In his message ([Image] How to identify images in an RDF context) du 9/02/05,
Karl Dubost wrote:
>I would like to have information about images. I have read a lot of 
>things about cataloging and creating images database in RDF, though 
>"nothing ready to use" for now ;) but something is still not solved 
>in my head.
>I'm taking a photograph with my digital camera. This image is 
>transfered to my computer with a JPEG format and contains already a 
>certain number of data like EXIF data.
>1. I can extract the EXIF data of this image and put in an RDF file 
>outside of the image, (not inside the image [see below])
>2. I can create more information, description, etc. That I add to this file.
>a. Is the good strategy one RDF file for one image? or an EXIF file? 
>and an geo file? and a description file?

The RDF guys so far, do not know what a file is ;-). So I have no 
answer to this question. I would say that it depends how convenient 
it is for you/your application.

>b. How do I identify the image ? a urn (which kind?) or an http uri?
>	<http://example.org/photo/2005/02/06/foo.jpg> even if the 
>image is not online.


>c. Images are between 1 and 3 Mo each, I keep them on DVDs or 
>external hard drive.
>	Can I use the previous identifier?

Yes please, do this. Its goal it to identify the thing, not to provide a path.

>d. I have many versions of the same image.
>	* Original Image (2000 x 3000 px)
>	* Thumbnail	(75 x 75 px)
>	* small version (400 x 600 px)
>	* cropped version
>	* published version in different context (different HTML 
>pages, web sites)
>	* Sampling (different images or part of the images associated 
>with others)
>All these versions share one part or all parts of the information 
>which is about the image. How do I define the model to identify it 
>and gives information about it?

What makes you thinks that there is diffent versions? Answer: they 
have something in common and yet they are different.

What is common is the work. What is different is the form (aka 
format, reproductions, instances...).

The suggestion is to have one URI identifying the work (topic, 
photographer, place...) and one URI per "instance" (thumbnail, ... or 
even file!). And to assert a relationship between them that the 
thumbnail is one "instance" of the work.

Think about what is a book, with translations, subsequent editions 
(with or without modifications), numbered and signed prints and the 
relation it has with a book in your library that has been borrowed by 

>e. Is it better to have a large RDF file with information of all 
>images? Or a small individual RDF file for each image?

See answer to question a.

>* RDF inside or outside the image.
>RDFPic recommends to put metadata inside the comment zone of JPEG. 
>XMP does it in the binary. In both case, I don't think it's always a 
>good idea, for privacy reason. Many softwares do not propose to wipe 
>metadata before publication on the Web. Problems will arise with 
>cell phones and GPS information.
>You may have information you don't want to publish on the Web. 
>Personal comments on the image, geo-localization of the image.
>Scenario: Someone is at a party at your place and likes very much 
>your painting or you computer. Cool. He takes a picture of it and 
>send it on his moblog, which displays the GPS information, then the 
>latitude and longitude with a comment "We are having so much fun at 
>Peter's place. He will write something about it on his weblog".
>Well no problems :))) Peter is leaving for holidays in Africa for 
>one month. Some people have noticed that. It's time for robbery !!! 
>We know the stuff inside, we know that Peter is not there. Let's go.
>That's one of the many possible cases and danger of information 
>contained in an image directly accessible to everyone. ;)

I think this is a totally different problem. Practical, actual, but 
something which is totally independent from picture stuff. Think of 
how much information any burglar can get from personnal web pages and 
knowing that people are not at home because obviously they will be 
presenting a very interesting paper at the other end of the world...

RDF empowers burglars with very interesting tools. But this does not 
really depends on wether the metadata are in or out of the picture.

Moreover, as you have seen in my answer, if you decompose between 
work and instance, you have the new answers that:
1) it is preferable to have the work described out of its particular instances;
2) of course it is useful to have the instance refering (from inside) 
to the work it is an instance of (by its URI);
3) it is the responsibility of the application to use this information or not.

  Jérôme Euzenat                  __
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Received on Thursday, 10 February 2005 10:45:47 UTC

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