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Re: exploring ambiguity via the "something-which-has" URI scheme

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 02 May 2003 12:29:01 -0400
Message-Id: <200305021629.h42GT1sf024391@roke.hawke.org>
To: Patrick.Stickler@nokia.com
cc: uri@w3.org, GK@ninebynine.org, phayes@ai.uwf.edu


Patrick Stickler writes
> This appears to be a URI scheme for expressing constellations
> of properties defined for an anonymous node (and not very unlike
> open-URIs).

I've never heard of "open-URIs" and I can't find anything relevant in
google.  Pointer?  It certainly seems similar to the "secure URI"
thread [1] going on in this list .  I was invoking RDF as a way to to
jump to the end of the arms-race for more general languages.

> I would think that what such URIs really denote would be the
> *class* of all resources which match those specified properties.

Ah, the ambiguity of natural language.  Yes, from my examples and the
way I named the scheme that would be a perfectly reasonable
interpretation.  As would the idea you feared, that I was proposing a
URI scheme where URIs did not have a single denotation.  But I defined
in otherwise.  I thought my text made that clear.

One the first point:

Let's call the two versions x-scheme-1 and x-scheme-2.  Each
x-scheme-1 URI denotes something for which the given RDF graph is
true.  Each x-scheme-2 URI denotes the class of things for which the
given RDF graph is true.  

   <x-scheme-1:foaf_mbox='connolly@w3.org';defpre(foaf_,http://xmlns.com/foaf/0.1/)>

denotes Dan Connolly, while

   <x-scheme-2:foaf_mbox='connolly@w3.org';defpre(foaf_,http://xmlns.com/foaf/0.1/)>

denotes the (singleton) class of things which are Dan Connolly.

Assuming the empty graph (always true) is written as the empty string,
and we can conclude:

   <x-scheme-1:> a rdf:Resource.      # it's something, but we
				      # have zero clue which thing

   <x-scheme-2:> a rdfs:Class.        # we at least know it's a class


I'm defining my strawman something-which-has URI scheme to be
x-scheme-1.  

(There's a naming challenge in making this clear in the scheme name.
Any grammatical phrase, like "individual-such-that" can still be read
as "(the class of) individual(s) such that".  Recent programming
conventions make the distinction using letter-case: must of us would
guess "redThing" denotes an individual which is red, "RedThing"
denotes a class of red things.  I also like the convention "redThings"
would denote a collection of individuals which are red, but sometimes
redThingList or redThingSet is necessary.)

One the second point: Consider the noun phrase "a red thing" in "I am
holding a red thing in my hand."  That noun phrase could denotes any
of a huge variety of things, but I'm using it to refer to a very
specific physical object.  URIs always refer to a specific thing,
even when no one happens to know anything about that thing.

> I think that it is (or should be) a fundamental presumption that,
> within the scope of the S/Web, a given URI consistently denotes
> a single thing.

Agreed.  I think Graham and Pat and you and I are in violent agreement
on this on this list.

But there are some tricky edge cases, which is what I am trying to
flesh out.  In particular, while agents may act as if a URI had one
true interpretation, they are only acting: we cannot, in general,
communicate interpretations.  At best, we can arbitrarily constraint
interpretations; that seems to be good enough for both humans and
machines.

> So if you tried to define a URI scheme that could
> intentionally be used to provide for overloading of denotation,
> I would consider that to be in conflict with the fundamental
> S/Web architecture.

I think it would also be in fundamental conflict with web
architecture, but ... I'm not sure how to phrase it for 2396bis.  My
last attempt [2] was ignored by everyone.  :-)

Here's another attempt, changing the basic definition of a URI.
Again, this goes somewhere near the beginning; exact glue can wait.

   Each URI is a string which conforms to URI syntax and which names
   something.  The naming relationship gives the URI its primary
   utility, allowing it to be transmitted in the place of something
   else.  There is no restriction on what kind of thing (real,
   imaginary, physical, conceptual, ...) can be named by a URI, but
   all such things are called "resources".  

   For a URI to be used effectively, the parties using it in
   communication often need to share a notion of which resource it
   names, but this commonality of knowledge does not need to be
   complete to be effective. In particular, human parties will tend to
   associate considerable real-world knowledge with the named
   resource, while software agents will simply maintain the facts
   about it suitable to their purpose.  In many cases there will be
   some ambiguity in communication using URIs because of incomplete
   sharing of knowledge about what is named by each URI, but this
   ambiguity can often be reduced as far as necessary.

   [ maybe say something about renaming and about indexical URIs like
   my.example.com?  something about GoodURIs having a long-term
   consensus of meanings.... ]

   In addition to serving as a name, each URIs can also serve as a
   message, conveying information about the named resource.  The
   language of the message is identified by the URI's scheme part, and
   to use the information encoded into the URI, an agent must
   recognize the scheme name and understand the corresponding
   language.  A common case is for the URI text to convey the network
   address of a server which can communicate authoritatively about the
   resource.

Or something....   Do you agree with what is stated there, even if you
disagree it has the best wording?

    -- sandro

[1] http://lists.w3.org/Archives/Public/uri/2003Apr/0095.html
[2] http://lists.w3.org/Archives/Public/uri/2003Apr/0062.html
Received on Friday, 2 May 2003 12:29:57 GMT

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