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Re: New Exif/RDF vocabulary

From: KANZAKI Masahide <mkanzaki@gmail.com>
Date: Tue, 12 Aug 2008 16:45:22 +0900
Message-ID: <834575810808120045r5d266693hadfe47896c473c59@mail.gmail.com>
To: "Tim Berners-Lee" <timbl@w3.org>
Cc: "SW-forum Web" <semantic-web@w3.org>, "Ivan Herman" <ivan@w3.org>, "Norman Walsh" <ndw@nwalsh.com>, "Karl Dubost" <karl@w3.org>

Tim, thanks for comments on Exif/RDF vocab.

> there is what seems to be an extra arc "exifdata" to a bnode labelled "Exif
> Image File Data", and then the exposureTime is a property of the exifdata,
> not of the original phototo.
> The arc seems to be used to group the data in the file, but I would find it
> more useful I think
> to define the exposureTime as a property of the picture itself.

Well, I've thought this point repeatedly, and chose to preserve the
data structure of Exif when model it for RDF. The reason is: the data
in Exif_IFD (e.g. exposureTime, fNumber, focalLength, etc.) represents
a sort of 'photo generating condition', not an attribute of an image
file. Notice that the sample image data is a JPEG file, which is not
the photo itself, but rather a compressed data of the original
photograph (which might be represented in RAW data). Your digital
camera can produce several image files with different quality and
resolution from a single 'photo'.

Maybe we should introduce some handy properties that apply those
'photo generating condition' attributes to the resulting image file.


> I would be inclined to use
>
>            exif:focalPlaneXResolution
>               [ exif:inches "9846.15384615" ];
>            exif:focalPlaneYResolution
>               [ exif:inches "9846.15384615"];
>
> You can the for example deduce what the exif:focalPlaneYResolution of
> something is in meters without any contradictions.
>
>
>            exif:focalPlaneXResolution
>               [ exif:inches "9846.15384615" ; unit:m "250.0"];
>            exif:focalPlaneYResolution
>               [ exif:inches "9846.15384615"; unit:m "250.0"];
>
> (Hmm .. in this example it looks as though the meters was probably the
> original figure!)

Yes, although these resolution values are not in 'length' but in
'pixels per unit', it could be. The current model, again, follows the
Exif data for simple processing. If we use this type of structured
representation, it could be:

         exif:focalPlaneXResolution
              [ exif:perInches "9846.15384615" ];

(not sure whether the term should be 'perInches' or 'perInch', but the
Exif spec says 'inches')

> > How stable is the http://www.kanzaki.com/ns/exif namespace?
> > Would you like a w3.org namespace for it?
> >
>
> There is already a w3.org exif namespace.
>        http://www.w3.org/2003/12/exif/

Since I have no way to maintain the W3C hosted resources, I cannot
update schema in that namespace. As I noted in previous message, I
chose to keep the above one intact for backward compatibility.

cheers,
-- 
@prefix : <http://www.kanzaki.com/ns/sig#> . <> :from [:name
"KANZAKI Masahide"; :nick "masaka"; :email "mkanzaki@gmail.com"].
Received on Tuesday, 12 August 2008 07:45:57 GMT

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