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RE: New version of URI Declarations [Usage scenarios]

From: Pat Hayes <phayes@ihmc.us>
Date: Sat, 1 Mar 2008 19:53:52 -0600
Message-Id: <p06230903c3efa8f4ecbf@[192.168.1.2]>
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>
Cc: "www-tag@w3.org" <www-tag@w3.org>
At 6:58 AM +0000 3/1/08, Booth, David (HP Software - Boston) wrote:
>  > From: Pat Hayes [mailto:phayes@ihmc.us]
>>
>>  At 2:23 AM +0000 2/29/08, Booth, David (HP Software - Boston) wrote:
>>  >Hi Pat,
>>  >
>>  >I think I see your point: without me standing in front of you,
>>  >pointing to the moon and saying: "I hereby declare that
>>  >http://dbooth.org/2007/moon/ henceforth refers to *that* moon", my
>>  >URI declaration cannot be guaranteed to be understood as referring
>>  >to the actual moon.
>>  >
>>  >That sounds like a valid point, but it doesn't invalidate the notion
>>  >of a URI declaration.
>>
>>  It does invalidate what you say about it, however. And I wonder quite
>>  what is the point of it, if it can't do what you say it is intended
>>  to do.
>
>I will try to improve the description.   I'm not well versed in 
>formal semantics, so any suggestions for improving the rigor and 
>precision of my explanations would be most welcome.
>
>The point of a URI declaration is to have a clear mechanism for a 
>URI minter to indicate to others what resource a URI is intended to 
>denote.  Operationally, it does this by indicating a particular set 
>of assertions -- the "core assertions" -- that should be accepted if 
>the URI is used.

Ive already pointed out the problem here. What is described in the 
second sentence can't possibly achieve what the first sentence says 
is the intended purpose. I'd suggest revising the statement of the 
intended purpose.

There is a problem (more down-to-earth) with the notion of 'should be 
accepted', as well. This sounds like its impossible to enforce, and 
worse, that there are going to be cases where it shouldn't be 
enforced. Suppose A publishes some rdf R and says it is a declaration 
of the URI x:y, and also says (perhaps using English or a controlled 
vocabulary) that x:y is supposed to denote, say, the moon; and 
suppose that R says that x:y is made of cheese. Are we supposed to 
accept this, just because this twit has called it a declaration?

>   These assertions are intended to delimit the range of possible 
>interpretations of what the denoted resource might be -- ideally 
>uniquely determining the resource, but (a) that depends on the 
>quality of the assertions, and (b) as you pointed out, ultimately 
>there is no way to ensure that a user's actual interpretation is the 
>same as the minter's intent.

Right, so the 'ideally' here isn't even an ideal: its impossible.

>
>>
>>  >Mechanically, a URI declaration really only creates an association
>>  >between a URI and a set of assertions (the "core assertions").
>>
>>  Well, OK, but now I would ask, why do we need anything special to do
>>  this? Publishing some OWL and giving the document a URI does this
>>  already. So whats so special about the new idea?
>
>The idea isn't new.  What's new is the term "URI declaration" and 
>the specific focus on what it is, why it is relevant and how it 
>should be used.
>
>>
>>  >The interpretation of those assertions as describing a particular
>>  >resource  -- whether you interpret them the same way I do -- is a
>>  >different issue.  That problem exists regardless of whether one
>>  >accepts the notion of URI declaration.  URI declarations do not try
>>  >to solve that problem.
>>
>>  So, what problem DO they solve?
>
>The notion of a URI declaration helps answer questions like the following.
>
>SCENARIO 1: Fred wishes to publish some RDF assertions about a 
>particular protein.  He notices that Alice, Beatrice and Carl have 
>already published assertions about the protein, and they all use the 
>same URI to denote that protein: the URI minted by Alice.  Fred 
>notices that if he uses Alice's URI to denote the protein, his 
>assertions will be logically inconsistent with some of Alice's 
>assertions, although they are logically consistent with Beatrice and 
>Carl's assertions.  He wonders whether he should publish his 
>assertions using Alice's URI -- and post a blog entry noting that 
>his assertions should not be used in conjunction with Alice's 
>assertions -- or mint a new URI.
>
>Question: Should Fred use Alice's URI?
>
>Answer: No.  He should mint a new URI and indicate the relationship 
>(not owl:sameAs) to Alice's URI -- at least rdfs:seeAlso.

Whoa. I think this is crazy. The scenario says that the URI denotes 
the protein, so lets accept that it indeed does. (The 'attachment' to 
the particular protein may be done for example by relating the URI to 
a standardized protein database accepted by the community.) If this 
is so, then the only way that Fred and Alice can be inconsistent is 
if they actually disagree about the facts of the matter. Perhaps Fred 
has a more up-to-date value for the molecular weight than Alice had, 
or something. But in this case, I think Fred should use the same URI 
to refer to the protein. Removing the inconsistency by using a 
different name is like saying: Oh, I guess we must be talking about 
different proteins, then. But they aren't, right? They are talking 
about the same thing, but they disagree on the facts. This is a case 
where some published RDF is *wrong*, and should be corrected: or at 
least, the real disagreement should be resolved.

>
>SCENARIO 2: Daria also wishes to publish some RDF assertions about 
>the same protein and wonders if she should mint a new URI.  She 
>notices that her assertions are logically consistent with Alice's 
>assertions, but not with Beatrice or Carl's.
>
>Question: Should Daria use Alice's URI?
>
>Answer: Yes, though she MAY mint a new one.
>
>SCENARIO 3: Erin has accumulated some observations about a different 
>protein, and she wishes to publish them as assertions.  Some of them 
>are merely assertions that serve to uniquely identify the protein 
>that she wishes to talk about.  Others are observations about the 
>protein's behavior.

Its not obvious that this distinction makes sense. Or at any rate, 
its not obvious that there is a particular category of facts that 
serve only to pin down reference.

>  She is very confident about the correctness of the first set of 
>assertions, but no so confident about the assertions about the 
>protein's behavior.  She mints a URI http://example/erin/proteins#p4 
>for the protein and wonders whether she should publish all of her 
>assertions in one OWL document at http://example/erin/proteins, or 
>separate them into two documents.
>
>Question: Should Erin put all of these assertions in a single document?
>
>Answer: No.  Erin should separate them into two documents.

Well, I agree that is good practice, but because she is more 
confident about some than about others. Thats the reason for the 
distinction, not that some pin down reference and others are mere 
facts.

YOu have assumed that the reference-nailing assertions are also the 
ones that are known with confidence, but that begs an important 
question. Consider a case where some empirical results are available 
which are very confidently true, but its not clear which protein they 
are relevant to (perhaps they were extracted from a biopsy which may 
have mixed two kinds of tissue: if this were genes instead of 
proteins, and we are talking about cancer typing, this is a real 
problem.) Now what do we 'declare' ?

Pat

>  The assertions that uniquely identify the protein should be placed 
>at http://example/erin/proteins, and should include an rdfs:seeAlso 
>that points to another document containing the other assertions.
>
>
>
>David Booth, Ph.D.
>HP Software
>+1 617 629 8881 office  |  dbooth@hp.com
>http://www.hp.com/go/software
>
>Opinions expressed herein are those of the author and do not 
>represent the official views of HP unless explicitly stated 
>otherwise.


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Received on Sunday, 2 March 2008 01:54:13 GMT

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