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+1 On Fri, Sep 13, 2013 at 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] >