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Don: As I understand it, the open world view implies knowledge not asserted for whatever reason, whereas sometimes a negative is a definite (and ultimately verifiable) fact, such as a painting simply not having a title. I think you're ultimately right about unknown things. Esmé's solution does seem to work, although would perhaps require redefinition for every element (title, place of pub, presence of clasp, binding, etc.). I did wonder if a more generic method existed. Thank you, Tom --- Thomas Meehan Head of Current Cataloguing Library Services University College London Gower Street London WC1E 6BT [log in to unmask] > -----Original Message----- > From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of > Donald Brower > Sent: 13 September 2013 14:46 > To: [log in to unmask] > Subject: Re: [CODE4LIB] Expressing negatives and similar in RDF > > 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]