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On 9/17/13 1:14 AM, Meehan, Thomas wrote: > Karen, > > Yes, I mean that if you have something like: > > - example:book1 dc:title example:unknownTitle . > - example:book2 dc:title example:noTitle . Thomas, this does not work because the object of dc:title is the title of the work (actually, the defintion is "A name given to the resource".) Therefore, you have just declared the title of the work to be "example:unknownTitle." That obviously isn't right, but most importantly it isn't helpful. It isn't just a question of dcterms requiring a literal, it has to do with the meaning of dc:title. You need a property with a different meaning. If you do this, then most dc-aware programs would display: Title: example:unknownTitle It would actually probably be more useful to say: dc:title "unknown title" although again you would be declaring that string to be the actual title of the item, which then gets us into the "Title varies" issue -- that is, you cannot prevent someone from creating a resource and giving it the actual title "unknown title." Now, if you were to have the object of dc:title defined as "Content as Text", then, as the conversation continued between Esme and I, you could have a blank text (which would be saying that dc:title = ""), and, since the object of dc:title would be a URI (not a string), you could potentially mint a new property with the semantics of "title status" that could take an object like "example:unknownTitle." kc > " > > then this approach only works for the dc:title element (putting aside for now what you said about dc:title requiring a literal). For any other elements you would need to define a similar example:unknownThing: > > - example:book2 example:claspNote "brass" . > - example:book2 example:claspNote example:noClasp . > > The same would go for the following approach: > > - example:book2 example:hasATitle egboolean:false . > - example:book2 example:hasAClasp egboolean:false . > > I hope these make sense. An approach that could be used for any element might be useful. I admit at this stage that I need to reread the second half of the thread again. I can't decide in my head if this is something that the rules (RDA, etc) should handle. If so, RDA in particular has an entertaining variety of ways of doing so. > > Thanks, > > 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 >> Karen Coyle >> Sent: 16 September 2013 16:23 >> To: [log in to unmask] >> Subject: Re: [CODE4LIB] Expressing negatives and similar in RDF >> >> On 9/16/13 2:05 AM, Meehan, Thomas wrote: >>> 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. >> >> Can you say more about what you mean by "redefinition for every element"? >> >> kc >> >> >>> 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] >> -- >> Karen Coyle >> [log in to unmask] http://kcoyle.net >> m: 1-510-435-8234 >> skype: kcoylenet -- Karen Coyle [log in to unmask] http://kcoyle.net m: 1-510-435-8234 skype: kcoylenet