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

On 12/05/2013 09:49 AM, Damian Steer wrote:
>
> On 5 Dec 2013, at 13:52, Thomas Steiner <tomac@google.com> wrote:
>
>> Dear Public-LOD,
>>
>> Thank you all for your very helpful replies. Following your joint
>> arguments, owl:sameAs is _not_ an option then.
>
> You could use dc:hasFormat to link them:
>
> "A related resource that is substantially the same as the
> pre-existing described resource, but in another format." [1]
>
> <http://ex.org/video.mp4> dc:hasFormat <http://ex.org/video.ogv> .

This is an excellent example in which perfection may be the enemy of the
good.  But it depends on the application.

For applications that do not semantically distinguish between mp4 and 
ogv formats of a work, owl:sameAs would be fine, because within the 
perspective of those applications, there would be no discernible 
difference between them.  But for other applications that *do* care 
about different formats, there would indeed be a difference and 
owl:sameAs should *not* be used.   So one might conclude that, to be 
safe, dc:hasFormat should always be used, or a proxy object should be 
used, because that would preserve the most information.   But notice 
that there is a cost in using dc:hasFormat or a proxy object instead of 
owl:sameAs : it requires a more sophisticated RDF application to 
understand the data.  owl:sameAs is completely generic, and doing 
owl:sameAs inference is probably one of the most common kinds of 
inference after subsumption (subclass) inference.  In contrast, 
dc:hasFormat is far more special-purpose, and the proxy object approach 
would require much more specific knowledge of the data to enable an 
application that treats mp4 and ogv formats as equivalent to recognize 
that -- for its purposes -- they are indeed equivalent.

Thus, for *some* purposes dc:hasFormat or a proxy object would be an 
overall better choice, and for *other* purposes owl:sameAs would be an 
overall better choice.  If you are publishing this data for others to 
use, you could offer both choices, putting the owl:sameAs statements in 
a separate document for those who want to use them.

David

Received on Thursday, 5 December 2013 15:59:08 UTC