W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > March 2003

RE: designating datatypes

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 4 Mar 2003 12:00:26 -0500
Message-Id: <p05111b05ba8a7f1ddafb@[64.134.139.17]>
To: Patrick Stickler <patrick.stickler@nokia.com>
Cc: w3c-rdfcore-wg@w3.org
>Pat,
>
>Person names are not globally unique. That's why
>we have identifiers such as social security numbers,so that we have 
>globally and temporally unique names.
>
>URIs are intended to be globally and temporally unique
>names.

The names are unique in the sense that they are proof against 
ambiguity about which name is which (unlike personal names, eg there 
are hundreds of people called "Pat Hayes").  They are not unique in 
the sense that they have a unique referent.

SS numbers (barring occasional bugs in the system) do have a unique 
referent, but the machinery which provides that uniqueness is 
elaborate and socially embedded,  requires a large degree of 
cooperation between many people over a long time period, and is 
influenced by national laws, for example.  If this social 
superstructure were not in place or were not operational, then SS 
numbers would not have unique referents. There are NO such mechanisms 
for URIrefs; the issue isn't even discussed in the relevant specs.

The closest that RFC 2396 comes is this:

"Resource
A resource can be anything that has identity.  ... Not all resources 
are network "retrievable"; e.g., human beings, corporations, and 
bound books in a library can also be considered resources.

The resource is the conceptual mapping to an entity or set of 
entities, not necessarily the entity which corresponds to that 
mapping at any particular instance in time.

Identifier
An identifier is an object that can act as a reference to something 
that has identity.  ...

Having identified a resource, a system may perform a variety of 
operations on the resource .... "

Notice the non-sequiteur at the end of this, where we have magically 
moved from 'can act as a reference' to being a means by which one can 
'identify' the referent, and then even more mysteriously, having 
identified it, one can perform operations on it. To see what is wrong 
with this, consider the fact that this sentence refers to Alpha 
Centauri, and I think I can say without risk of being thought 
overconfident, actually manages to refer to said astronomical body; 
but I wouldn't expect the ability to refer to a star would give me 
the ability to perform any operations on it. If I were to say that 
Julius Caesar probably saw Alpha Centauri, then Ive referred to 
something that I certainly cannot perform any operations on, since 
his atoms have long since been spread thinly over the entire planet.

>
>If the RDF MT does not reflect that, then it is IMO
>fatally flawed.

Its not a flaw to fail to do the impossible.

>Let's discuss this in Boston... (hopefully you're
>attending the plenary)

I'm here right now :-)

Pat
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Received on Tuesday, 4 March 2003 12:00:31 EST

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