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Re: a test case for "literals must be self-evident"

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 10 Dec 2001 11:13:12 -0600
Message-Id: <p05101016b83696e99d3f@[65.212.118.193]>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org
Sorry this reply is delayed.

>OK, I blathered on about this requirement in...
>
>   literals must be self-evident
>   Dan Connolly (Wed, Oct 17 2001)
>   http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Oct/0338.html
>
>but recent discussion with Peter S. and Jeremy made me realize
>I can reduce this to a real simple entailment test:
>
>Does dte-blunt.nt entail dte-pointy.nt?
>
>dte-blunt.nt:
>
>   <http://example/x> <http://example/y> "abc".
>
>dte-pointy.nt:
>
>   <http://example/x> <http://example/y> "abc".
>
>i.e. does an RDF document entail itself?
>Surely the answer is yes, right?
>I suggest that P/P++ do not guarantee this entailment;
>they fail to specify that the answer to this
>test is "yes".
>

Well wait a minute. Are those the SAME graph, or two different but 
isomorphic graphs? Do you mean, does a document entail *itself*, or 
does it entail any other document with the same lexical form? In the 
P++ scheme, distinct literal nodes are treated as syntactically 
distinct entities, so the answer matters.

For example, suppose that we were to merge these two graphs. Would 
the result contain two triples or one? If the answer is one, then 
they are the same document and this document entails itself (of 
course). If the answer is two, then they are two distinct but similar 
documents, and the answer then is, indeed, no in the P++ scheme, 
since those two different literal occurrences might be typed 
differently.

But this, seems to me, does not violate the guidelines you enunciated 
in 
http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Oct/0338.html 
since there you talk about an interpretation being CHANGED - 
redefined - by the addition of information. Here, nothing is being 
changed; if you add datatyping information, you are simply 
disambiguating the bare literal by adding more information about it, 
by removing some of its (datatyped) interpretations. This is just 
like normal RDF inference, right? The only difference is that every 
occurrence of a bare literal has to be treated as a separate 
syntactic entity. That gives inference a slightly unusual 'feel' on 
bare literals, perhaps, but it isn't anything disastrous. There is no 
nonmonotonicity, if you stick to the rules.

Pat
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Received on Monday, 10 December 2001 12:13:10 EST

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