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RE: Issue i0001 - Clarification of "identifier"

From: Steve Graham <sggraham@us.ibm.com>
Date: Tue, 14 Dec 2004 13:58:57 -0500
To: "Srinivas, Davanum M" <Davanum.Srinivas@ca.com>
Cc: "David Booth" <dbooth@w3.org>, public-ws-addressing@w3.org, public-ws-addressing-request@w3.org
Message-ID: <OFB3714E7D.1AB39CA3-ON85256F6A.0063EEF7-85256F6A.00684468@us.ibm.com>
I believe it is true that for any "identifier" its usefulness to determine 
"sameness" or difference between two resource instances must be done in 
some context.  For example, all the resources in my company (ie behind my 
company's firewall) may use the same value set for <muws-xs-1:ResourceId/> 
of the resources exposed.  Therefore the interpretation of 
<muws-xs-1:ResourceId/> used in EPRs referencing my company's resources 
must be done in the context of my companies services.  Note, however, that 
the resourceID is not specific to a particular address.  Consider, for 
example, I have one resource, identified by 
<muws-xs-1:ResourceId>sggRes1</muws-xs-1:ResourceId>.  Consider also that 
I have two Web services that can act upon that type of resource.  WS1 
provides base manageability characteristics (such as state property 
retrieval), and one Web service provides notification capabilities.  These 
two Web services may be deployed at different endpoint addresses (value of 
wsa:Address in EPR is different), but each EPR may have the exact same 
value for <muws-xs-1:ResourceId/>.  In this case, the ResourceID is not 
specific to an address, but rather it is specific to another context, that 
being "my organization".

Does this help?

Steve Graham
(919)254-0615 (T/L 444)
STSM, On Demand Architecture
Member, IBM Academy of Technology
<Soli Deo Gloria/>

"Srinivas, Davanum M" <Davanum.Srinivas@ca.com> 
12/14/2004 01:04 PM

Steve Graham/Raleigh/IBM@IBMUS
"David Booth" <dbooth@w3.org>, <public-ws-addressing@w3.org>, 
RE: Issue i0001 - Clarification of "identifier"

ResourceId is specific to an "Address". right? don't u need both to be 
able to converse with the resource?
-- dims

From: Steve Graham [mailto:sggraham@us.ibm.com] 
Sent: Tuesday, December 14, 2004 1:00 PM
To: Srinivas, Davanum M
Cc: David Booth; public-ws-addressing@w3.org; 
Subject: RE: Issue i0001 - Clarification of "identifier"

Isn't this the case that the <muws-xs-1:ResourceId/> is the identifier and 
the EPR is still simply a reference?  That is the EPR is not an 
identifier, but rather it contains an identifier? 


Steve Graham
(919)254-0615 (T/L 444)
STSM, On Demand Architecture
Member, IBM Academy of Technology
<Soli Deo Gloria/>

"Srinivas, Davanum M" <Davanum.Srinivas@ca.com> 
Sent by: public-ws-addressing-request@w3.org 
12/14/2004 12:54 PM 

"David Booth" <dbooth@w3.org>, <public-ws-addressing@w3.org> 

RE: Issue i0001 - Clarification of "identifier"

For those who want to make "EPRs be usable as "identifiers" in the
other, mathematical sense of the word", they can add the muws
ResourceId[1] (<muws-xs-1:ResourceId/>) as a Reference Property[2]. 


-----Original Message-----
From: public-ws-addressing-request@w3.org
[mailto:public-ws-addressing-request@w3.org] On Behalf Of David Booth
Sent: Monday, December 13, 2004 12:15 AM
To: public-ws-addressing@w3.org
Subject: Issue i0001 - Clarification of "identifier"

Unfortunately, the word "identifier" has more than one meaning. 

I believe Paco and Jeff are correct that there is a mathematical sense
of the word "identifier" in which identifiers are required to be unique,
i.e., if two identifiers are different, then they cannot refer to the
same thing.  (I cannot easily locate a citation for this sense of the
word, but I seem to remember this being discussed on the www-tag list at
w3.org a couple of years ago.)

I (and I think most members of the WS Addressing WG, judging by the
minutes of last week's meeting) have been using the word "identifier" in
the Web Architecture or programming language sense of the word, in which
two different identifiers can indeed refer to the same value, thing or
Web resource.

RFC 2396 defines the word "identifier" as:
  An identifier is an object that can act as a reference to
  something that has identity.  In the case of URI, the object is
  a sequence of characters with a restricted syntax.

Issue #1 is about the use of URI+RefProps in the RFC 2396 / WebArch /
programming language sense of the word: something that can act as a
reference to a Web resource.  In this context, the words "address" or
"reference" would be just as good.  (Then again, we may discover
ambiguities with those terms also!)

If anyone is interested in having EPRs be usable as "identifiers" in the
other, mathematical sense of the word (such that different "identifiers"
MUST reference different resources), then that should be raised as a
separate issue.


David Booth
W3C Fellow / Hewlett-Packard
Received on Tuesday, 14 December 2004 18:59:32 UTC

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