At a theoretical level, doesn't the Open World Assumption in RDF rule out
outright negations? That is, someone else may know the title, and could
assert it in a separate RDF document. RDF semantics seem to conflate
unknown with nonexistent.

Practically, Esme's approach seems better in these cases.


-Don


--
Donald Brower, Ph.D.
Digital Library Infrastructure Lead
Hesburgh Libraries, University of Notre Dame




On 9/13/13 8:51 AM, "Esmé Cowles" <[log in to unmask]> wrote:

>Thomas-
>
>This isn't something I've run across yet.  But one thing you could do is
>create some URIs for different kinds of unknown/nonexistent titles:
>
>example:book1 dc:title example:unknownTitle
>example:book2 dc:title example:noTitle
>etc.
>
>You could then describe example:unknownTitle with a label or comment to
>fully describe the states you wanted to capture with the different
>categories.
>
>-Esme
>--
>Esme Cowles <[log in to unmask]>
>
>"Necessity is the plea for every infringement of human freedom. It is the
> argument of tyrants; it is the creed of slaves." -- William Pitt, 1783
>
>On 09/13/2013, at 7:32 AM, "Meehan, Thomas" <[log in to unmask]> wrote:
>
>> Hello,
>> 
>> I'm not sure how sensible a question this is (it's certainly
>>theoretical), but it cropped up in relation to a rare books cataloguing
>>discussion. Is there a standard or accepted way to express negatives in
>>RDF? This is best explained by examples, expressed in mock-turtle:
>> 
>> If I want  to say this book has the title "Cats in RDA" I would do
>>something like:
>> 
>> example:thisbook dc:title "Cats in RDA" .
>> 
>> Normally, if a predicate like dc:title is not relevant to
>>example:thisbook I believe I am right in thinking that it would simply
>>be missing, i.e. it is not part of a record where a set number of fields
>>need to be filled in, so no need to even make the statement. However,
>>there are occasions where a positively negative statement might be
>>useful. I understand OWL has a way of managing the statement This book
>>does not have the title "Cats in RDA" [1]:
>> 
>> []  rdf:type owl:NegativePropertyAssertion ;
>>     owl:sourceIndividual   example:thisbook ;
>>     owl:assertionProperty  dc:title ;
>>     owl:targetIndividual   "Cats in RDA" .
>> 
>> However, it would be more useful, and quite common at least in a
>>bibliographic context, to say "This book does not have a title". Ideally
>>(?!) there would be an ontology of concepts like "none", "unknown", or
>>even "something, but unspecified":
>> 
>> This book has no title:
>> example:thisbook dc:title hasobject:false .
>> 
>> It is unknown if this book has a title (sounds undesirable but I can
>>think of instances where it might be handy[2]):
>> example:thisbook dc:title hasobject:unknown .
>> 
>> This book has a title but it has not been specified:
>> example:thisbook dc:title hasobject:true .
>> 
>> In terms of cataloguing, the answer is perhaps to refer to the rules
>>(which would normally mandate supplied titles in square brackets and so
>>forth) rather than use RDF to express this kind of thing, although the
>>rules differ depending on the part of description and, in the case of
>>the kind of thing that prompted the question- the presence of clasps on
>>rare books- there are no rules. I wonder if anyone has any more wisdom
>>on this.
>> 
>> Many thanks,
>> 
>> Tom
>> 
>> [1] Adapted from
>>http://www.w3.org/2007/OWL/wiki/Primer#Object_Properties
>> [2] No many tbh, but e.g. title in an unknown script or indecipherable
>>hand.
>> 
>> ---
>> 
>> Thomas Meehan
>> Head of Current Cataloguing
>> Library Services
>> University College London
>> Gower Street
>> London WC1E 6BT
>> 
>> [log in to unmask]