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Re: What if an URI also is a URL

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 11 Jun 2007 16:09:17 -0500
Message-Id: <p06230910c293645374d0@[10.100.0.28]>
To: Tim Berners-Lee <timbl@w3.org>
Cc: "M.David Peterson" <m.david@xmlhacker.com>, "r.j.koppes" <rikkert@rikkertkoppes.com>, "Yuzhong Qu" <yzqu@seu.edu.cn>, "Sandro Hawke" <sandro@w3.org>, <semantic-web@w3.org>, <swick@w3.org>, "John Black" <JohnBlack@kashori.com>

Tim, as this discussion gets to the heart of what 
Ive been trying to argue for several years, 
please take the comments below as intended in a 
spirit of analysis rather than just pins and 
angels.

>On 2007-06 -11, at 13:53, John Black wrote:
>
>>
>>Tim Berners-Lee wrote
>>>
>>>
>>>On 2007-06 -09, at 21:22, M. David Peterson wrote:
>>>
>>>>On Sat, 09 Jun 2007 07:13:52 -0600, Tim Berners-Lee <timbl@w3.org>
>>>>wrote:
>>>>
>>>>>No. It cannot identify both a document and a person.
>>>>
>>>>Tim: Will all due respect... WTF?
>>>
>>>
>>>I am using the 'identify' in the strict sense of 'denote'.
>>>The semantic web is like a logic language in which URIs are symbols.
>>
>>Do you believe that by claiming to use the 
>>strict, logical sense of the word 'denote' you 
>>thereby cause or require such denotations to be 
>>absolute and unambiguous? Where do think 
>>denotations (or identifications) come from?
>
>The architecture is that each URI is owned.

OK

>  With HTTP URIs, this happens through the domain 
>name system and often  delegation within a 
>domain. Unlike a word, a URI has an owner.  The 
>owner attempts to make enough information 
>available that the URI can be used by others 
>without ambiguity in practical situation.

Well now, several points. First, do owners in 
fact do this? I havnt seen a great deal of such 
information-providing going on, myself. But OK, 
fair enough: perhaps you mean, they SHOULD make 
such information available. But second, more 
seriously, HOW would they do this? Take your 
example:

>For example, W3C owns 
>http://www.w3.org/People/Berners-Lee/card#i and 
>has delegated to me the right to say what that 
>URI stands for.

OK. So, what DOES that URI stand for? How will 
you tell someone what the referent is that you 
intend it to denote, so that they know what to 
use it for? Now of course, you and I being smart 
human native English speakers who are reasonably 
tech-savvy can look at this and figure out that 
it is probably meant to refer to you. But really, 
that does depend on us being this smart and 
savvy. It isn't absolutely obvious: and there are 
many, many web pages out there which I really 
have no idea what their owners would say they 
denote.

>To use it for something else is an error.

But surely if you make this ruling then it is up 
to you to tell me enough about what it is 
supposed to be used for, so that I can know when 
Im making an error. HOW??  And what about a URI 
that I own and wish it to denote, say, the planet 
Venus, or my pet cat? What do I do, to attach the 
URI to my intended referent for it?

>>
>>In my opinion to denote (or to identify) is a 
>>verb, something that is done by the users of a 
>>symbol. After all, symbols (URI) are not 
>>agents, they don't wake up and choose to denote 
>>this or that.
>
>They have wonders which create them for a specific purpose.

wonders/owners I presume.

But the key question to me is, how can they 
communicate the purpose to the reader? How does 
one publish an intention? How does one indicate a 
referent, other than by describing it? How much 
description is enough?

>>Nor do I think denotation is an attribute or 
>>property of a symbol, somehow built in or 
>>attached when the symbol is first conceived. It 
>>is more like a dance. I use a symbol to denote 
>>something expecting you to interpret it to 
>>denote the same thing. And this coordination, 
>>this synchrony of interpretation by both sender 
>>and receiver, is not always easy. It requires 
>>real effort to sustain it. The minter of a URI 
>>cannot make it happen by declaration, nor can a 
>>research group or a standards body just decree 
>>it so.
>
>In many cases, the URI is defined by connection 
>to already well-defined sets of things.  In 
>other cases, such as the terms in the OWL 
>ontology, there was a huge amount of effort and 
>discussion involved, and the current term is 
>supported by a lot of ongoing tutorials and so 
>on.  No one said it was easy.  But it is a 
>different architecture from dance associated 
>with natural language words.

The huge effort was for defining the meanings of 
the OWL reserved vocabulary, and that is indeed 
about as defined as a vocabulary can get. But if 
we just take some OWL ontology and ask how well 
it constrains the meanings of the new URIs that 
occur in it, this is *very* much like the word 
dance that John refers to. In fact in all 
essentials it seems to me to be pretty much the 
same game. I publish (say) some stuff which I 
intend to mean something, you read (hear) it and 
get some insight into my meaning. You draw some 
conclusions and if you send (tell) them to me I 
can check to see if I agree and if not try to 
send (say) some more to you to make your grasp of 
my intentions more firm.

It HAS to be similar, barring machine telepathy. 
There really isn't anything that either people or 
machines can do much beyond send symbols to one 
another: and symbols carry meaning only 
imperfectly, with inherent ambiguity.

>
>It is different by design.  The semantic web is 
>an engineered system, not an observation of 
>nature.

But it is a real system, and so it has to obey 
laws of nature. And there are laws of meaning as 
well as of physics.

>
>>The reason this matters is that since it 
>>requires this effort to create a 
>>denotation/identification in the first place, 
>>it is far more sensible, to me at least, to 
>>expect that the final disambiguation of a 
>>symbol be accomplished in the same way, by 
>>coordinated effort of the parties using the 
>>symbol, not by declaration of the W3C 
>>specifications that all URIs be absolutely 
>>unambiguous.
>>This seems to me to be, as my grandfather used to say, a vain task.
>
>Your grandfather would perhaps have suggested 
>that an attempt to define the meaning of common 
>words, as the Académie Française is set up to do 
>were a 'vain task'.   Many would agree.  But 
>given that his water came to him though pipes 
>connected, possibly, by half-inch British 
>Standard pipe-thread connections, and he rode on 
>rails set a certain distance apart by some 
>committee, and his TV came for better or worse 
>in 525 or 625 lines as decided by other 
>committees, he may have respected that the 
>creation of standards is a very valuable 
>function, and an essential to progress.
>
>When people meet to define W3C specifications 
>they are not doing it out of vanity.   They are 
>performing coordinated effort of the parties who 
>would like to be able to use the symbol.  They 
>are, in general, users and representatives of 
>users of the symbol.   They come together to 
>allow those who follow them to use it. They 
>often work long hours, receiving inadequate 
>recognition for either products shipped or 
>papers published, the conventional metrics of 
>performance, so I would not call it vanity.

The point surely is that URIs used to refer (not 
as in HTTP, but as in OWL) do *not* have a 
standardized meaning. Standards are certainly a 
chore to create, but they only go so far. OWL 
defines the meanings of the OWL namespace, but it 
does not define the meanings of the FOAF 
vocabulary, or the URIrefs used in, say, 
ontologies published by the NIH or by JPL. The 
only way those meanings can be specified is by 
writing ontologies: and finite ontologies do not 
- cannot possibly - nail down referents 
*uniquely*. No amount of authority-delegating or 
standard-setting is going to change this basic 
fact.

Pat



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Received on Monday, 11 June 2007 21:09:31 UTC

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