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

RE: erratum Re: resources and URIs

From: Bullard, Claude L (Len) <clbullar@ingr.com>
Date: Mon, 28 Jul 2003 09:48:23 -0500
Message-ID: <15725CF6AFE2F34DB8A5B4770B7334EE022DC6BF@hq1.pcmail.ingr.com>
To: "'pat hayes'" <phayes@ihmc.us>
Cc: www-tag@w3.org

Taking some time to clean up inbox:

From: pat hayes [mailto:phayes@ihmc.us]

>OK, thanks for that. I agree that the letter/address/envelope analogy 
>makes perfect sense, and is consistent with the architecture. 
>Unfortunately it is not consistent with the other claim, that URIs 
>*denote* resources, that 'identifies' means 'refers to' rather than 
>'can be used to access' (in some suitably general form).

Yes.  The most common use of the URI is to identify a server for 
getting or sending a representation/state to/from.  Unless the 
"can be a bot" argument cites a representation, the language 
isn't consistent.

>It is tough to say the address on the envelope
>is the content of the letter, but that is the
>way the post office sees it.

>Actually that is not how the post office sees it, nor the legal arm 
>of the government. 

Actually, unless they open it, that is the way they see it.  That 
is the content they handle.  The fact of enclosure makes the letter 
inside opaque, and for all the reasons you cite.

>>The system conflates address with content.

>The post office doesn't; are you saying the Web does? I see no reason 
>for this claim: can you elaborate on it?

See above.  The address is the content as far as the post office 
as handler is concerned.  Of course that breaks down when a 
PO is required by law to open an enclosure and inspect it.

>>That sleight of hand is fundamental to the
>>web architecture which uses mapped locations
>>as addresses

>Yes

>>then addresses as names.

>Where? How? I would be grateful if you could explain why this is 
>fundamental to the architecture. If you are right, then I may be 
>missing something important.

Because the types of servers are not known to the architecture. 
It names them, but unless the http morph is recognized specifically 
as a handler type, it's just a name.  So people are free to put 
the URI on the side of a bus; it's just a name.   I agree this 
stretches the 'architecture' to limits that include galaxies 
(and even Ford Falcons), but that is what has been attempted 
and that is why the web architecture has these apparent inconsistencies. 
It attempts to include anything that can be named as part of 
its domain.  One might consider that *ambitious*.

>>The address still makes sense to everyone but
>>the letter carrier.  He can't drop off, and
>>since nothing is mailing from that address,
>>there is no problem because he returns it as
>>undeliverable.

>Actually, in Florida, he just throws it away and doesn't tell anyone. 

That explains the last Presidential election results in Florida.

>Unless its a magazine he wants to read, of course, then he keeps it, 
>reads it, and then throws it away. The address I gave did not make 
>sense. The 1400 block of W. La Rua St. makes sense, but not 1404. 

It makes lexical sense.  As I said, the provable properties of 
URIs sans a system handler is their syntax.

>Nothing is gained by inventing nonexistent things for them to 
>designate when they do not designate anything.

Nothing is lost.  System returns error.

>There isn't any better definition than
>some resource is on the web if it has
>a URI and is not on the web if it doesn't
>because the web is and always has been
>fundamentally, a system using an addressing
>system.

>Let me paraphrase.  A URI is a URI if it is a URI. Does that amount 
>to the same observation? Seems to me to say about the same thing, 

A URI is a URI if it conforms to the syntax definition.  Full stop. 
A meaningful URI may require it to name something which exists. 
A URI with meaning to a system of addressing should return a value. 
The nature of that value to a user isn't known until the act of retrieval 
occurs.  It isn't any deeper than that.  The identity of the 
thing retrieved depends on the act of identification.

>In your excellent analogy, this is like analyzing the postal service 
>by saying that every address *must* be the address of some unique 
>delivery box. 

Only if used by a system that requires a URI to be an address.

>When faced with the manifest falsity of this claim, the 
>response is to say that even if there is no delivery box at that 
>address, we will just invent a virtual delivery box to be the 
>delivery box of that address, because every address *must* have a 
>delivery box, by fiat, even when there is no box there to be the 
>delivery box: it is required by the architecture.

Nope.  The architecture requires it to return an error if 
no box at that address is found.  It might exist offline, 
but the system regards that as error by definition.  It 
might be online tomorrow.  That is a problem of 'existence' 
in an active process; it's temporal.

>>Saying it is on the web means it
>>has a valid address and a route to that is
>>possible if not guaranteed.

>A route to something nonexistent is not possible, pretty much by the 
>meaning of 'exist' and 'route'.

See above.  The address can be valid and possible; it may 
not be active.  It may not ever be active, but that is 
as you say, the nonsense of a pointer to zero.  Works 
as a placeholder, but does little.  A null value is 
still a value in the notation.

>>Uniqueness of identity is proven in terms
>>of a process of identification; it makes
>>no useful sense otherwise.  It is a provable
>>or unprovable property but it is only a
>>problem in the question of the proof.
>>The SW has some real issues with proof.
>>And it always will have if any provable
>>property relies on analogical proofs.

>You have lost me there. Im afraid. There is no need to prove 
>uniqueness of identity: that amounts to the observation that x=y 
>implies x=y.

I mistate.  The identity value has to be assigned 
to a unique object by a process of identification. 
In the real world, this may involve using other 
values to build a case that this object is the 
object to which the system assigned this identifier.
When letting prisoners out of lockup, several 
properties are checked to build that case including 
physical properties of the individual, the documented 
process of which cells they have occupied, and so on.
When a car is chopped, it is difficult to trace the 
origin of parts, so the manufacturer puts the unique 
string (a VIN: a multimorph string whose individual 
morphs are meaningful with regards to origin, model, 
etc.), on several hidden locations.  Again, without 
a process of identification, identifiers can be 
meaningful with respect to their lexical composition, 
but not to the object to which they are assigned.

len
Received on Monday, 28 July 2003 10:48:30 UTC

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