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LC Comment, Section 2 (or is it 2.0?)

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Fri, 5 Mar 2004 22:18:59 +0100
Message-Id: <B7FA4F44-6EEA-11D8-BF98-0003939E0B44@isr.umd.edu>
To: public-webarch-comments@w3.org

(This is just on the part of section 2 up to 2.1)

"""Parties who wish to communicate must agree upon a shared set of 
identifiers and on their meanings."""

This is false. A baby communicates distress and discomfort to his or 
her parents without there being any identifers, or even any 
identification going on on the part of the baby. I might be able to 
communicate that  this large bolder crushing my leg should be removed 
by the stout and helpful non-english-speaking lass beside me by making 
somewhat spastic gesticulations. Or, in a more structured way, I might 
point at the bolder, or wap the bolder, and make a little rolling 
motion with my hands.

"""The ability to use common identifiers across communities motivates 
global identifiers in Web architecture."""

This makes me feel parse-challenged. The *ability* to use common 
identifiers motivates global identifiers? Why? How?

On the one hand, I value the effort at terseness the TAG clearly made 
in this document. But, reading this I feel lost. This *little* bit of 
narrative is so elliptical to leave me no better off.

The third paragraph seems to provide *some* explication, in that I 
guess I should be motivated by the power gained from the vastness of 
the choice (though, frankly, I hate tons of choice).

"Thus, Uniform Resource Identifiers ([URI], currently being revised) 
which are global identifiers in the context of the Web, are central to 
Web architecture."

(Editorial) I'll just point out that four paragraphs later:
	"""The scope of a URI is global; the resource identified by a URI does 
not depend on the context in which the URI appears (see also the 
section about URIs in other roles). """"

This reuse of "context" in contrary ways is confusing.

""""Constraint: Identify with URIs

The identification mechanism for the Web is the URI.""""

Presumably this isn't *quite* right, as there is a need for some 
idenification mechanisms that are not URI based in order to associate 
(some, at least) URIs with resources for subsequent reidentification. 
Also, for example, host names identify things very critical to the 
functioning of the web, and yet, aren't URIs. Etc.

"""A URI must be assigned to a resource in order for agents to be able 
to refer to the resource. """

Even restricted to software agents, this is false.
	_x foaf:mbox <mailto:bparsia@isr.umd.edu>.

Allows an OWL Reasoner to refer to me (since foaf:mbox is an 
InverseFunctionalProperty). (While there was a URI involved, it wasn't 
assigned *to me*.) I can make or refute assertions about me in this 

"""Resources exist before URIs; """

If URIs are strings, and string are abstract mathematical entities 
(i.e., a kind of data structure) independant of their physical 
instantiation, then, reasonably, URIs have always existed, so any 
particular URI has existed before some recently come into existent 
Resources. I'm not even sure of the point of such metaphysical 
statements. Or imagine I have, oh, a programming language where I have 
URI objects (a subclass of String). Let's say I want to use a URI to 
identify some other objects in my system. Does this claim require that 
(in pseudopython):

	my_object_uri = URI('http://blahblah.com/blah') #The URI now exists!
	my_funky_object = FunkyObject() #Now the Resource in question exists.

is broken in some way? Why would this matter?

"""a resource may be identified by zero URIs.""""

Ah, this is what you mean? It's not very happy either. I take it you 
mean that some resource might *not* be identified by *any* URI. Cool. 
And given my above example, it might still be possible for agents to 
refer to it. Naturally, it's often a good idea to give various 
resources a URI! For example, I don't think it's possible (or, at 
least, easy) to *link* to something in a machine readable way in HTML. 
So, give such resources URIs, please. I think it's quite possible to 
make the sensible point without appeal to broken metaphysics.

Actually, the rest of the paragraph seems quite good and sensible.

"""Principle: URI assignment

A resource owner SHOULD assign a URI to each resource that others will 
expect to refer to.""""

I would recommend the TAG study FOAF because that community has made a 
different choice (i.e., to rely a lot on inverseFunctionalProperties).

Aside from that, I think this  principle misses an important point: 
Formats and protocols should (often?) be designed to use URIs. This 
encourages URI assignment by adding value to such assignment.

Bijan Parsia.
Received on Friday, 5 March 2004 16:18:56 UTC

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