W3C home > Mailing lists > Public > www-tag@w3.org > July 2003

Re: resources and URIs

From: pat hayes <phayes@ihmc.us>
Date: Mon, 21 Jul 2003 17:07:36 -0500
Message-Id: <p06001a04bb420dab8046@[]>
To: "Jonathan Borden" <jonathan@openhealth.org>
Cc: www-tag@w3.org

>pat hayes wrote:
>>  >>
>>  >>  On this picture, the information (which Dan, in your introductory
>>  >>  example, reads on his screen, and which is in some sense all about the
>>  >>  weather in Oaxaca) is a representation of the (current state of) some
>>  >>  entity *in the WWW itself*: a resource in the global information
>>  >>  network: the state of some computer system, or maybe some abstraction
>>  >>  of a computer system.
>>  >>
>>  >>  However, it is also clear that neither the weather in Oaxala, nor
>>  >>  Oaxala itself, are entities of this kind:
>>  >
>>  >it is?
>>  Yes, it is. That is, the category of things that can be actually "on"
>>  an information network in the sense of being physically connected to
>>  it does not encompass things like regions of Mexico, or weather.
>If we accept the postulate that resources which are 'on the Web' are those
>with a URI, suppose a new URI scheme "photo" which to skip the details of
>any specific implementations, has a protocol that results in a digital
>photographic representation when dereferenced.

OK, then in the sense I was understanding the word "on" here, its the 
*representation* which is on the network, not the thing it is a 
picture of.  But I realize now that others are using 'on the Web' to 
mean what I would phrase as 'referred to somewhere on the Web'. The 
problem for me that is not that this is meaningless, exactly, but 
that it is useless. Being 'on the Web' in this sense isn't 
well-defined, cannot be checked for accuracy, provides no 
architectural or semantic content.  So OK, I don't give a damn 
whether something is or is not 'on' the Web in this sense, and I see 
no reason why I or anyone else should give a damn what the TAG group 
thinks about it either, as it makes no difference to anything.

>I know I am stretching your
>current conceptions of information network, but surely you are aware of
>optical networking, and I know you have sufficient ability to generalize the
>concept of an information networks to something beyond ethernet over copper.
>For example RFC 1149.

I really don't mind having my network ideas stretched by technology, 
but I do rather jibe at the 'network' terminology extending right out 
to encompass arbitrary references of any kind, because then the 
entire universe is a 'network' and we have just drifted off into 
general systems theory or something equally nebulous and useless. I 
thought we were talking about *architecture*.

>  >
>>  >  >   weather and cities in Mexico are not the kind of entities which can
>>  >>  be thought of as 'objects on the networked information system'.
>>  >
>>  >Yes, they are; I think of them that way.
>>  OK, then you are apparently able to think in a way that is not
>>  accessible to me. Could you elucidate this way of thinking, at all?
>>  For example, is there *anything* that, in your way of thinking, could
>>  not be part of an information network? Is there any distinction, in
>>  your way of thinking, between being in some sense physically attached
>>  to an information system, being an entity transferred over an
>>  information network, and being referred to by a symbolic expression
>>  stored in an information system?
>I can certainly accept those distinctions. It's the "physically attached to
>an information network" that I can be rather flexible with -- for example I
>*am* physically attached to such a network at the moment my fingers are
>pecking at my keyboard

Not in the interesting sense that I can (potentially) do something to 
you by means of a transfer protocol.

>... but suppose you are sitting with a laptop
>connected to a network via wireless ... is that a physical connection?

Sure. Electromagnetic waves are physical.

>>  >  >  Other examples abound,
>>  >>  eghttp://chandra.harvard.edu/photo/2003/ngc1068/index.html  is in
>>  >>  clearly about a galaxy containing a supermassive black hole, which is
>>  >>  also not something one would expect to find as part of an networked
>>  >>  information system, given the likely physical constraints on network
>  > >>  architecture.
>>  >
>>  >I think that particular identifier refers to a document about
>>  >a galaxy, not the galaxy itself; if you want to refer to
>>  >the galaxy itself, you should use a URI with a # in it.
>>  I know this general rule: it makes some sense of the usage which has
>>  emerged for the SW languages. But you are talking about *referring
>>  to*; whereas my point was about being *part of* a network. I agree
>>  that a URI reference might well refer to a galaxy: but - and this was
>>  my point in sending the message - that doesn't seem to be anything
>>  like the same claim that a galaxy is *part of* an information network
>>  or (to refer for a moment to the language used in RFC 2396) that by
>>  having a URI reference which refers to the galaxy one is thereby
>>  enabled to *perform operations on* the galaxy.
>Why not? If I shine a light on a galaxy, I am not performing operations on

Actually, no.  Chances are that the galaxy won't be there when your 
photon arrives.

>Sounds like quantum computing to me :-) Seriously, what actual
>distinction are you making? If you mean 'network' as defined by a finite set
>of hardware and software specifications, which we can list, then our concept
>of 'network' will be outdated before it is published given the apparent rate
>of new networking products and specifications. My own definition of
>information network would include electronic, photonic, biological and
>chemical processes.

Mine also. I don't mean to restrict the kinds of process involved.

My goodness, this seems so obvious, but it is incredibly hard to get 
the point across.  Its a very simple basic, point about language and 
representations.  Just referring to something doesn't of itself 
establish any kind of causal link to it. (Isnt that just kind of 
obvious??) It doesn't enable you to access it, send signals to it , 
perform operations on it, transfer information to or from it, etc.. 
It doesn't, in fact, enable you to DO anything at all, except refer 
to it.  Its not AT ALL like the relationship between an memory 
address and the contents of the location addressed, or a file name 
and the file, or an identifier in a program and the datastructure it 
identifies.  And the reason its not like that is because the universe 
is not a computer: it doesn't have an addressing scheme or a file 
structure or an environment on a stack somewhere to get your names 

So, in a nutshell: reference has got nothing to do with architecture. 
Imagine a scifi scenario in which there is a solar burp, or 
something, and the planet gets irradiated with something that neatly 
switches off all human left temporal lobes, so we all wake up one 
morning totally dyslexic and aphasic. We have no idea what the hell 
our web pages are saying to us: all the semantics has been erased. 
Now, we humans would be in quite a pickle, no doubt: but the Web 
would work *in exactly the same way*. If you click on a URI in your 
browser window, all the http protocols will do their thing and some 
page will appear on your screen: if you click on a mailto: URI then a 
mail window will appear and if you hit some keys then emails will get 
delivered, all just like now. The *architecture* of the Web will be 
undamaged. Of course, it will not then be the slightest use, nothing 
will refer to anything any more; but the architecture will still be 
working. So the semantics is irrelevant to the architecture.

>Of course I'd prefer to define an architecture that is
>still relevent in 10 years.

So would I.  But the way to do that is not to start by getting the 
semantics confused.


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Received on Monday, 21 July 2003 18:07:39 UTC

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