Re: Is the same video but in different encodings the owl:sameAs?

On Dec 4, 2013, at 11:24 AM, Thomas Steiner <tomac@google.com> wrote:

> Hi again,
> 
> Thanks for your reply, Kingsley.
> 
>> <http://ex.org/video.mp4> denotes one entity.
>> <http://ex.org/video.ogv> denotes another.
> 
> We agree on that. I guess my question boils down to "how to avoid
> having to make duplicate statements about each resource"? I cannot
> take your proposed <#CapturedEventNameX> as a "proxy" entity, as it is
> not a video, but an event.
> 
> My argument was more: take any random user and let them view the .ogv
> and the .mp4 versions of the video, and if they say it is the same
> (which random users most probably will do, as the visual and the
> audial contents are the same), the two versions can be considered
> owl:sameAs.
> 
> One version may, e.g., have more details (say, due to the bit rate)
> than the other, just like the two entities below are considered
> owl:sameAs, even if one _may_ have more, or more accurate, facts than
> the other…
> 
> <http://dbpedia.org/resource/London> owl:sameAs
> <http://rdf.freebase.com/ns/en.london>
> 
> Does that make sense?

The official semantics of owl:sameAs is that the two IRIs on either side of it refer to the very same thing. So it is fine for one of them to link to something with more facts than the other, but those facts have to be facts **about the same thing** out there in the world (such as London, capital city of the UK). A good test of whether an owl:sameAs triple is correct would be, can you say *anything* using the subject URI that would not be true if you said it with the object URI, or vice versa? If not, then that might be (probably is) a good sameAs. But if you can, then it is definitely not a good sameAs. This is a stronger test than your "same movie" test. Owl:sameAs is "same movie, same edition, same creation date, same anything you can think of". It is the absolute, final, in-the-limit absolutely-one-and-the-same identical relationship, and it does not allow for any "yes, but" or 'well, nearly" or "in a sense, but not in another sense" or "well, for all practical purposes" qualifications. 

But as I say, that is the *official* semantics. 

Pat Hayes

> 
> Thanks,
> Tom
> 
> -- 
> Thomas Steiner, Employee, Google Inc.
> http://blog.tomayac.com, http://twitter.com/tomayac
> 
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Received on Wednesday, 4 December 2013 22:18:08 UTC