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

No, that symbol contains the full scope over which you've known your dad,
plus anything you've learned about him before. However, there are narrower
contextual scopes in which you may make specific claims about that may not
always be true (my Dad when I was 12, for instance).

Jim


On Sun, Mar 17, 2013 at 12:51 AM, Alan Ruttenberg
<alanruttenberg@gmail.com>wrote:

> 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
>>
>


-- 
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