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 <escow...@ucsd.edu> "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" <t.mee...@ucl.ac.uk> 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 > > t.mee...@ucl.ac.uk
