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Is a namesapce a resource? - was: duck

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 6 Jun 2000 10:07:39 -0400
Message-ID: <008401bfcfc0$934bebc0$a60a1712@col.w3.org>
To: "John Cowan" <cowan@locke.ccil.org>
Cc: <xml-uri@w3.org>

-----Original Message-----
From: John Cowan <cowan@locke.ccil.org>
To: Tim Berners-Lee <timbl@w3.org>
Cc: xml-uri@w3.org <xml-uri@w3.org>
Date: Saturday, June 03, 2000 3:56 PM
Subject: Re: URIs quack like a duck


>Tim Berners-Lee scripsit:
>
>> Therefore, your home page is a namespace.
>
>Wow.  Now I begin to understand where you are coming from.  You actually
>do believe, then, that a namespace can *be* a document.

What I actually said was that a namespace (to be useful) is a resource.
[You can discuss what a "document" is I suppose - a resource or an entity
body?]

But what I think you mean is it is something of which it is useful to
ask for a rendition.

Like the W3C logo.  Its URI is
http://www.w3.org/Icons/WWW/w3c_home
If you ask our server you will not get the logo.  The logo is an abstract
thing.
The server will give you a rendition -- or possibly some metadata about
another
resource which is in fact a valid rendition of the logo.


> But if so,
>why can't a namespace *be* an Internet mailbox?  (Since the Namespace
>Rec tolerates either).  Presumably because you can't fetch an entity
>body for a mailbox.


No: you don't *have* to be able to fetch an entity bodu for a namespace.

Because you know that for anything in the mailbox: namespace you can queue a
posted message to it.
There is a certian semantics of mailboxes.
Namespaces do not support these semantics.  You can't email to them.

But more than that: the question if you take a step back is clearly absurd:
"why can't a namespace be a mailbox?".  Just in natural langugae you
can see that they are completely diffeernt concepts.

>Me, I see a namespace as belonging to an entirely different ontological
>class from a document.  I no more identify a namespace with a document
>than I identify a document with a brick.


I see that.  You could say that it is like a person.  Normally a person is
identified
indirectly by a property such as a mailbox or a home page.
In RDF, you can say that a person who has mailbox ora@w3.org has hair-color
blond.
Which is good enough.  We could do that with namespaces.
Through all this I am not exactly sure what your meaning of "document"
is.  I could imagine a world in which resources were namespaces
or documents or mailboxes and so on,  but I think I would find the term
"document"
difficult to define.  Once you have languages for talking about languages,
then you cannot separate the system into layers of"documents",
"metadocuments".


We could of course reduce to absurdity the argument that namespace should
not actually be abstract things which you candirectlty represent, by using
the same argument on anything which you think of as a document.
What is the member list of W3C?
It is a list of organizations wo are members of W3C.
It has a URI, http://www.w3.org/Member/List
If you requests a rendition of that resource, you will get, at the moment,
an entity body which is in HTML 4.0 document which may be a few minutes
out of date and be imperfect in some ways but it is definitive, and uses
anchor tags and links and an unordered list to represent the information.
You could argue that the HTML document is not actually the list,
but is some information about the list. It is a rather arbitrary subset
of the information, perhaps, just as a schema is an arbitrary subset
of information about a namespace.

This is what I meant when I said that a dictionary is a book: a namespace
is a resource. If you admit to a namespace being something you can actually
represent
yes, just like a document, then you  get great power, and generality.

(The ironic thing is that in the XML level all that one says about a
language
is its syntax.  We have a number of languages such as xml-schema coming
along which
allow one to describe the syntactic constraints of a language. So at the XML
level, where we have the most resistance to the idea, there already is
all the apparatus we need for self-defining documents. At higher levels such
as RDF the assumption that documents are self-describing is not in question,
even though we don't yet have common languages for inference rules.)

>I suppose you would counter that accessing http://www.w3.org doesn't
retrieve
>a document per se, but only a representation of a document....


You chose "document" to be "resource", then yes.
After all, if you set your browser preferences to French, who knows what
will happen.
The entity body you get changes with many things - time, for example.

>It seems that the longer we talk, the deeper the divisions that surface.


How important it then is to talk.

Maybe it is that he concpet of self-describing documents just does not
exist for many people.  While I can understand that not everyone would
put there energy I had not anticipated that there would be an actual
resistance
to identifying namespcaes as resources.

Tim


>--
>John Cowan                                   cowan@ccil.org
> Yes, I know the message date is bogus.  I can't help it.
> --me, on far too many occasions
>
Received on Tuesday, 6 June 2000 10:06:19 GMT

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