- From: Jim McCusker <mccusj@rpi.edu>
- Date: Sat, 16 Mar 2013 12:43:57 -0400
- To: David Booth <david@dbooth.org>
- Cc: Jeremy J Carroll <jjc@syapse.com>, Umutcan ŞİMŞEK <s.umutcan@gmail.com>, Kingsley Idehen <kidehen@openlinksw.com>, w3c semweb HCLS <public-semweb-lifesci@w3.org>
- Message-ID: <CAAtgn=Tr9W8-8RaOzGWvcYkDm_=-N-qyBmQEK_76eNC5wyxfhQ@mail.gmail.com>
I see "A URI denotes only one resource" as a rule of the game that makes it far more interesting than if we don't accept that rule. If I find that someone is violating that rule, I'll kick them out of my game (exclude their graph). Jim On Sat, Mar 16, 2013 at 12:37 PM, Jim McCusker <mccusj@rpi.edu> wrote: > I'm not terribly interested in a Humpty Dumpty interpretation of the web > of data. That's part of the motivation for having global identifiers like > URIs/URLs. There's no point in merging ANY graphs under this view, since > you have no way of knowing if the referents are the same. I'm not saying > that people don't denote different things with the same URI, I'm saying > that, by using a URI that someone else controls, you are accepting their > denotation of it. > > Jim > > > On Sat, Mar 16, 2013 at 12:30 PM, David Booth <david@dbooth.org> wrote: > >> Hi Jim, >> >> You are in good company in thinking that a URI always denotes the same >> resource, because that is a widespread misconception. (I call it Myth #1 >> in http://dbooth.org/2010/**ambiguity/paper.html<http://dbooth.org/2010/ambiguity/paper.html>.) But it simply is not true in the RDF semantics. >> >> The Architecture of the World Wide Web blithely states that "By design a >> URI identifies one resource": >> http://www.w3.org/TR/webarch/#**id-resources<http://www.w3.org/TR/webarch/#id-resources> >> But this is an architectural goal -- not the reality of RDF semantics. >> Although it is a good goal, and helpful as a guide to URI users, it turns >> out to be an oversimplification of reality. >> >> The RDF Semantics is very clear that a URI denotes one resource only in >> *one* interpretation of a *given* RDF graph: >> http://www.w3.org/TR/rdf-mt/#**interp<http://www.w3.org/TR/rdf-mt/#interp> >> But we do not have only one, giant, global RDF graph -- see Myth #2 -- we >> have *many* graphs. And in general, a given RDF graph admits *many* >> satisfying interpretations. The RDF semantics does not require that a URI >> denote the same resource in *different* graphs or in *different* >> interpretations of the same graph. >> >> Thus, although as an architectural goal we would *like* a URI to always >> denote the same resource, the reality is that a URI can -- and often does >> -- denote *different* resources in different graphs, and this can cause >> inconsistencies when graphs are merged, as illustrated in Figure 26: >> http://dbooth.org/2010/**ambiguity/paper.html#**inconsistent-merge<http://dbooth.org/2010/ambiguity/paper.html#inconsistent-merge> >> >> That is precisely why it is helpful to keep different perspectives in >> different graphs, as Jeremy suggested. >> >> David >> >> >> On 03/16/2013 01:08 AM, Jim McCusker wrote: >> >>> David, >>> >>> The problem with this is that by definition, URIs ALWAYS denote the same >>> resource. If there is doubt that you might be denoting something other >>> than what a resource is, you should be defining your own resource. >>> >>> Jim >>> >>> >>> On Sat, Mar 16, 2013 at 12:35 AM, David Booth <david@dbooth.org >>> <mailto:david@dbooth.org>> wrote: >>> >>> Hi Umutcan, >>> >>> You have indeed stumbled on a deep question, and I think Jeremy's >>> suggestion is exactly right. This paper on "Resource Identity and >>> Semantic Extensions: >>> Making Sense of Ambiguity" illustrates how owl:sameAs works in RDF >>> semantics: >>> http://dbooth.org/2010/__**ambiguity/paper.html#sameAs<http://dbooth.org/2010/__ambiguity/paper.html#sameAs> >>> >>> <http://dbooth.org/2010/**ambiguity/paper.html#sameAs<http://dbooth.org/2010/ambiguity/paper.html#sameAs> >>> > >>> >>> There are two keys to understanding owl:sameAs. One is to answer >>> the question: what RDF graph are you considering? The other is to >>> understand that the same URI may denote different things in >>> different RDF graphs. It is only when RDF statements are in the >>> *same* graph that the RDF semantics requires the URI to denote the >>> same resource. That is why the question of what graph you are >>> considering is crucial, and why Jeremy suggested keeping the >>> different perspectives in different graphs. >>> >>> FYI, the above paper also explains how you can "split" the identity >>> of an RDF resource if you need to merge RDF graphs that use the same >>> URI in contradictory ways. >>> >>> David >>> >>> >>> >>> On 03/15/2013 02:29 PM, Jeremy J Carroll wrote: >>> >>> I did not find this a rookie question at all. >>> >>> This seems to get to the heart of some of the real difficult >>> issues in Semantic Web. >>> >>> My perspective is different from yours, and a resource >>> description that I author is a description of the resource from >>> my perspective; a resource description that you author is a >>> description from your perspective. >>> >>> If I have some detailed application that depends in some subtle >>> way on my description, I may want to ignore your version; on the >>> other hand, a third party might want to use both of our points >>> of view. >>> >>> One way of tacking this problem is to have three graphs for this >>> case: >>> >>> Gj, Gu, G= >>> >>> Gj contains triples describing my point of view >>> Gu contains triples describing your point of view >>> G= contains the owl:sameAs triples >>> >>> Then, in some application contexts, we use Gj, sometimes Gu, and >>> sometimes all three. >>> >>> Jeremy >>> >>> >>> >>> >>> On Mar 15, 2013, at 11:02 AM, Umutcan ŞİMŞEK >>> <s.umutcan@gmail.com <mailto:s.umutcan@gmail.com>> wrote: >>> >>> Thanks for the quick answer : ) >>> >>> So this issue is that subjective for contexts which allows >>> to use owl:sameAs to link resources if they are not >>> semantically even a little bit related in real world? >>> >>> Sorry if I'm asking too basic questions. I'm still a rookie >>> at this :D >>> >>> Umutcan >>> >>> >>> On 15-03-2013 19:38, Kingsley Idehen wrote: >>> >>> On 3/15/13 1:05 PM, Umutcan ŞİMŞEK wrote: >>> >>> My question is, does LODD use owl:sameAs properly? >>> For instance, are those two resources, >>> dbpedia:Metamizole and drugbank:DB04817 (code for >>> Metamizole), really identical? Or am I getting the >>> word "property" in the paper wrong? >>> >>> The question is always about: do those URIs denote the >>> same thing? Put differently, do the two URIs have a >>> common referent? >>> >>> ## Turtle ## >>> >>> <#i> owl:sameAs <#you>. >>> >>> ## End ## >>> >>> That's a relation in the form of a 3-tuple based >>> statement that carries entailment consequences for a >>> reasoner that understand the relation semantics. Through >>> some "context lenses" the statement above could be >>> accurate, in others totally inaccurate. >>> >>> Conclusion, beauty lies eternally in the eyes of the >>> beholder :-) >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> -- >>> Jim McCusker >>> Programmer Analyst >>> Krauthammer Lab, Pathology Informatics >>> Yale School of Medicine >>> james.mccusker@yale.edu <mailto:james.mccusker@yale.**edu<james.mccusker@yale.edu>> >>> | (203) 785-4436 >>> >>> http://krauthammerlab.med.**yale.edu<http://krauthammerlab.med.yale.edu> >>> >>> PhD Student >>> Tetherless World Constellation >>> Rensselaer Polytechnic Institute >>> mccusj@cs.rpi.edu <mailto:mccusj@cs.rpi.edu> >>> http://tw.rpi.edu >>> >> > > > -- > Jim McCusker > Programmer Analyst > Krauthammer Lab, Pathology Informatics > Yale School of Medicine > james.mccusker@yale.edu | (203) 785-4436 > > http://krauthammerlab.med.yale.edu > > PhD Student > Tetherless World Constellation > Rensselaer Polytechnic Institute > mccusj@cs.rpi.edu > http://tw.rpi.edu > -- Jim McCusker Programmer Analyst Krauthammer Lab, Pathology Informatics Yale School of Medicine james.mccusker@yale.edu | (203) 785-4436 http://krauthammerlab.med.yale.edu PhD Student Tetherless World Constellation Rensselaer Polytechnic Institute mccusj@cs.rpi.edu http://tw.rpi.edu
Received on Saturday, 16 March 2013 16:44:40 UTC