Hi Douglas,
> I understand your set of three triples - that XYZ (a
> collection) has a thumbnail relationship with
> http://.../image/333 (a DCMIType=Image), but what if the
> object in the thumbnail relationship is not a URL but an
> embedded bitstream? It still has a type of Image, but I
> really need to know whether I should be looking in it for a
> URI scheme plus colon or extracting the whle thing as a
> bitstream. DC CD AP doesn't require cld:logo to be a URI/URL
> so I should be able to embed a bitstream in my implementation
> of the AP (not that I'm saying I necessarily will)?
Oh goodness, you don't 'alf ask some 'ard questions! ;-)
I think this would be an example of what the Abstract Model calls a
"rich value".
As for how to represent it in RDF/XML... eek! The following is very
tentative as I'm pretty much at the limits of my knowledge of XML and
datatyping here.
I guess in that XML you'd have to use some mechanism to indicate that
your content is encoded binary data, and XML Schema has a datatype so
_maybe_ you can do something like:
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:dcmitype="http://purl.org/dc/dcmitype/"
xmlns:some="http://example.org/some/"
>
<dcmitype:Collection>
<some:thumbnail>
<dcmitype:Image>
<rdf:value
rdf:datatype="http://www.w3.org/2001/XMLSchema#base64Binary">123456789
<!-- encoded bitstream here -->
</rdf:value>
</dcmitype:Image>
</some:thumbnail>
</dcmitype:Collection>
</rdf:RDF>
The triples from this look OK to me, but I admit I'm pretty much out of
my depth here and I think you really need to ask an RDF/XML expert this
question!
> I'm not quite sure of the extra triple you would add to
> indicate this (if indeed it is possible)? This is why I used
> the XLink stuff to allow for richer specification of the
> link, though I realise I may have erred slightly - I was sure
> it validated as RDF OK when I dreamed it up last year, though
> possibly it's only valid at a syntax level rather than at a
> semantic level??
It is valid RDF/XML in the sense that it passes the RDF validator and
generates a set of triples, but I suspect that is only by chance! I have
no idea what information the graph conveys i.e. what the predicates in
those triples "mean", because - as far as I know - XLink isn't defined
in terms of RDF properties.
Pete
