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owl:sameAs - Is it used in a right way?

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Sun, 17 Mar 2013 00:51:08 -0400
Message-ID: <CAFKQJ8nzF2q8EMRuS3JormvoVvJiiyRYGuuN93LBaUWmgBCDmA@mail.gmail.com>
To: Erich Gombocz <egombocz@io-informatics.com>
Cc: Jim McCusker <mccusj@rpi.edu>, David Booth <david@dbooth.org>, 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>
My dad's name is Danny. I've known him a Long time, during which he's
changed a lot. Am I supposed to stop calling him dad because he's not
precisely the same as he was when I was 10?

-Alan

On Sunday, March 17, 2013, Erich Gombocz wrote:

> Observing this discussions for quite a while, I have to say that I fully
> agree with Jim’s comments - unless you can assert that the referent is
> the same AND the contextual scope is the same, it should not have the same
> URI as it does not *precisely *describe the same thing.****
>
> ** **
>
> Cordially,****
>
> Erich****
>
> ** **
>
> *From:* Jim McCusker [mailto:mccusj@rpi.edu]
> *Sent:* Saturday, March 16, 2013 9:35 PM
> *To:* David Booth
> *Cc:* Jeremy J Carroll; Umutcan ŞİMŞEK; Kingsley Idehen; w3c semweb HCLS
> *Subject:* Re: owl:sameAs - Is it used in a right way?****
>
> ** **
>
> Hmm. In the end, all three of them are talking about the same apple.
> Either a) the apple changed (they do that), or b) someone got it wrong (Is
> a McIntosh a red apple or green apple? It's kind of both).****
>
> ** **
>
> This of course goes to my general assertion that most of the time,
> disjointness assertions are more likely to be wrong than right, but this
> isn't about that. There is an apple, and all three people agree they are
> talking about the same apple. It may have changed, or someone was color
> blind, or looking at a colorized black and white photo when they decided
> what color it was. This is, more than anything, why, unless you know that
> the referent is that same AND the contextual scope is the same, it's better
> to mint your own URI and link out using altOf and specOf, rather than
> making assertions using someone else's resource.****
>
> ** **
>
> Jim****
>
> ** **
>
> On Sun, Mar 17, 2013 at 12:20 AM, David Booth <david@dbooth.org> wrote:***
> *
>
> Hi Jim,****
>
>
>
> On 03/16/2013 12:37 PM, Jim McCusker wrote:****
>
> I'm not terribly interested in a Humpty Dumpty interpretation of the web
> of data.****
>
> ** **
>
> Well, you'd better get used to it, because that interpretation is standard
> RDF Semantics. I don't think it's going away any time soon.****
>
> ** **
>
> That's part of the motivation for having global identifiers
> like URIs/URLs.****
>
> ** **
>
> Exactly! That's why the idea that "a URI identifies one resource" is "a
> good goal, and helpful as a guide to URI users", even though it is not
> actually true.****
>
> ** **
>
> There's no point in merging ANY graphs under this view,
> since you have no way of knowing if the referents are the same.****
>
> ** **
>
> Not true! Don't throw the baby out with the bath. When you merge graphs,
> you force the referents to be the same. Sometimes the merge works fine, and
> sometimes the merge becomes inconsistent. Just because you cannot *always*
> merge two graphs without causing inconsistency does not mean that merging
> is pointless. It just means that *some* graphs can be merged and others
> cannot. That is only a problem if your expectations of being able to merge
> any two graphs are set unrealistically high.****
>
> ** **
>
> 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.****
>
> ** **
>
> You're preaching to the choir on that one! I certainly agree with that
> architecture, but that is only part of the story. The problem is that there
> is inherent ambiguity about the resource that a URI denotes. This is
> inescapable. And it means that two different, well-intentioned RDF authors
> can reasonably interpret a URI's resource identity differently, and those
> differences can cause conflicts to show up when their graphs are merged.
>
> As a simple example, suppose Owen, a URI owner, mints a URI :apple to
> denote an apple. As the URI's owner, he defines the URI's resource identity
> using the following RDF statements:
>
> # Owen's definition of :apple
> @prefix : <http://example/owen/> .
> :apple a :Apple .
>
> Arthur, a URI author, then publishes his own RDF statements about Owen's
> apple (standard prefix definitions omitted for brevity):
>
> # Arthur's statements about Owen's apple
> @prefix : <http://example/owen/> .
> :apple a :GreenApple .
> :GreenApple rdfs:subClassOf :Apple .
>
> Note that Arthur's statements are entirely consistent with Owen's
> definition of :apple .
>
> Now Aster, another URI author, also publishes some RDF statements about
> Owen's apple. She also uses Owen's apple definition, but has no knowledge
> of Arthur's statements. Aster writes:
>
> # Aster's statements about Owen's apple
> @prefix : <http://example/owen/> .
> :apple a :RedApple .
> :RedApple rdfs:subClassOf :Apple .
> :RedApple owl:disjointWith :GreenApple .
>
> Note that Aster's statements are also consistent with Owen's definition of
> :apple.
>
> Finally, Connie, an RDF consumer, discovers Arthur and Aster's graphs and
> wishes to merge them. Unfortunately, the merge is inconsistent,
>
> It is tempting to assume that someone did something "wrong" here. For
> example, one might claim that Owen's definition was ambiguous, or that
> Arthur and Aster should not have made assumptions about the color of Owen's
> apple if Owen did not state the color in his definiti
>
Received on Sunday, 17 March 2013 04:51:36 UTC

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