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Re: Clarifying what a URL identifies (Four Uses of a URL)

From: Sandro Hawke <sandro@w3.org>
Date: Fri, 24 Jan 2003 02:15:49 -0500
Message-Id: <200301240715.h0O7Fnn27171@wadimousa.hawke.org>
To: "Larry Masinter" <LMM@acm.org>
cc: www-tag@w3.org


Larry Masinter writes:

>    indicates(context) (URI)  -> Concept

I'm a little fuzzy on what you mean by context.   Would it be fair
to simply have several different kinds of indicator functions and drop
the notion of context?   

> The definition of a URI scheme should define the
> 'identifies' function; it cannot easily define
> any 'indicates' functions. For 'http', the 'identifies'
> function winds up being "whatever you connect to
> by sending HTTP messages to the server designated by
> the host:port of the URI, using the path of the URI,
> at the time that the 'identifies' function is invoked
> by an interpreter."

What do I connect to when I GET http://www.w3.org?   It's not a
computer (there are lots of them answering at that address), it's not
an Apache process (there are lots of them answering on each machine),
...  Is it a file?  Is the kernel which handles the file?  That file
gets checked out of CVS whenever it's changed -- is it the CVS server?
Heck, is it the person who last modified the file?

I'm not being facetious -- I really can't get a grip on a particular
conceptual thing when you say "whatever you connect to."  What I can
mentally grip is shared memory locations [1], although I realize
that's just another abstraction [2].   I think you're going for the
"communications end-point" model [3], which feels very natural and
right until I look closely.

> In this model, 'identifies' is construed narrowly.
> But the range of 'indicates' can be quite broad.

Yeah, that all sounds good to me.

> RDF uses an 'indicates' function. When I use
> http://www.w3.org to talk about the World Wide Web
> Consortium or the web server or a web page at
> a particular point in time -- in each case, this
> is a different context for the 'indicates'
> function.

Hrm.  None of those are the "identifies" function?   This starts to
sound like RDF uses a many-to-many mapping, which isn't very helpful.

I'm happy with one identifies function and one indicates function.  My
problem with RDF is that you can't tell which its using sometimes.

    -- sandro

[1] http://lists.w3.org/Archives/Public/www-tag/2003Jan/0315.html
[2] http://lists.w3.org/Archives/Public/www-tag/2003Jan/0319.html
[3] http://www.w3.org/2003/01/web/#endpoints
Received on Friday, 24 January 2003 02:18:05 GMT

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