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

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Fri, 29 Mar 2013 00:52:55 -0400
Message-ID: <CAFKQJ8mAFiyNGpze7w_38UHh6hgzEqS7xF5MLWv58Qknp5kOiQ@mail.gmail.com>
To: David Booth <david@dbooth.org>
Cc: Oliver Ruebenacker <curoli@gmail.com>, "public-semweb-lifesci@w3.org" <public-semweb-lifesci@w3.org>
>
>     Let's say I have a graph G1 containing two statements s1 and s2.
>>>
>> Both s1 and s2 contain the same uri u1. Do you think the RDF specs
>> allow me to use interpretation I1 for s1 and interpretation I2 for s2?
>>
>
> If you are asking whether the spec tells you how to determine the truth
> condition of I1(s1) and the truth condition of I2(s2), then yes. Whether s1
> and s2 happen to be contained in G1 is irrelevant.  If s1 and s2 are ground
> triples, the relevant rule in the section 1.4 is:
>
>   if E is a ground triple s p o. then I(E) = true if
>   s, p and o are in V, I(p) is in IP and <I(s),I(o)> is in IEXT(I(p))
>   otherwise I(E)= false.
>
> If you are asking whether the spec tells you how to determine the truth
> value of I(G1), for some interpretation I based on I1 and I2, where I1 !=
> I2, then the answer is no.  The spec does not define any way to combine
> interpretations.


Right. Nothing about combining, nothing about switching.


> Could it then be true that u1 in s1 refers to a different thing than
>> u1 in s2?
>>
>
> Yes, of course, if I1 != I2.


He meant at the same time. You answer here as if the question was: Are
those two things the same color (and they are), and you say, no they might
not be, if you wear yellow glasses while looking at the one and blue
glasses while looking at the other. Of course if you wear the same glasses
looking at both you see the same thing.

Similarly, l1 has u1 meaning the same thing in both cases, and l2 has u1
meaning the same thing in both cases. So the answer to his question is "no".


> Even though both occurrences are in G1?
>>
>
> It doesn't matter where they occur.  The rules have no
> context-sensitivity.  If you give the rule an interpretation I1 in which u1
> maps to "fish", and a ground triple s1, then the rule gives you the truth
> value of I1(s1) with u1 mapping to "fish".  If you give the rule an
> interpretation I2 in which u1 maps to "bird", and a ground triple s2, then
> the rule gives you the truth value of I2(s2) with u1 mapping to "bird".
>  There is nothing magic about it, and no dependency whatsoever on s1 or s2
> occurring or not occurring in any graph.
>

That makes it sound like the interpretation could vary across graphs, which
it can't.


> On the other hand, as mentioned above, the spec does *not* tell you how to
> determine the truth value of a graph containing s1 and s2 using both I1 and
> I2 (assuming I1 != I2).  It only tells you how to determine the truth value
> of a graph containing s1 and s2 using a *single* interpretation.


Right, because that's what "interpretation" means. It similarly does not
tell you anything about how to determine the truth value of different
graphs with different interpretations.


>    I'm not interested in whether this is a useful approach, or whether
>> you would do it this way. I just want to know whether you think the
>> specs allow this.
>>
>
> Yes, of course the specs allow this.  Those semantic rules can be applied
> to *any* interpretation and *any* graph or triple.


This is misleading. You can't pick pairs of (interpretation, graph). You
can pick an interpretation first, and then apply that interpretation to all
graphs.

If you change the interpretation, you change it in all graphs. So in
changing the interpretation, u1 no longer refers to whatever it did before,
and the answer to his question is "no".


> It all comes down to the fact that, in essence, the RDF Semantics spec
>>> defines a function -- call it RS -- of *two* arguments: one
>>> interpretation
>>> and one graph
>>>
>>
What is this function RS?  Please call it by it's actual name so we can
look it up. If you are suggesting RS is the interpretation function, then
no, it always takes single argument. Sometimes that argument is a uri,
sometimes a triple, sometimes a graph.


>      I'm still waiting to hear why one argument needs to be a graph.
>>
>
It doesn't, assuming "it" is the interpretation function. We'll see what's
the case once we know what "RS" is.

-Alan
Received on Friday, 29 March 2013 04:53:54 UTC

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