OWL contains some negative assertions, as Thomas noted. Nothing prevents
anyone else from negating your negative, however, in that Open World.
Assuming that we have provenance on statements, then you might be able
to make sense of two conflicting bits of information.
I've found two vocabularies that do a Boolean negation (Not, as well as
And and Or):
http://vocab.deri.ie/csp
http://vocab.deri.ie/ppo#
The CSP is used for car models, where there can be hundreds of options
on a car (color, radio, #doors, gps, etc etc). However, looking at the
diagram [1] I think it would take me great concentration to figure out
what they are doing (not to mention their weird use of the term
"Fluent"). I'm going to look for examples but am not sure how to do that
- hunt and peck, I guess.
kc
[1] http://vocab.deri.ie/csp#Not
On 9/13/13 6:46 AM, Donald Brower wrote:
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" <[email protected]> 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 <[email protected]>
"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" <[email protected]> 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
[email protected]
--
Karen Coyle
[email protected] http://kcoyle.net
m: 1-510-435-8234
skype: kcoylenet
