[ogsa-naming-wg] Response to public comment

[David Snelling]

Folks,

I have posted the attached response to the comment raised by Philippe  
Le Hegaret.

The comment was:


>> It is in fact contained in the Web Services Addressing
>> 1.0 specification itself:
>> [[
>> The Architecture of the World Wide Web, Volume One [AoWWW] recommends
>> [AoWWW, Section 2] the use of URIs to identify resources. Using  
>> abstract
>> properties of an EPR other than [destination] to identify  
>> resources is
>> contrary to this recommendation. In certain circumstances, such a  
>> use of
>> additional properties may be convenient or beneficial; however, when
>> building systems, the benefits or convenience of identifying a  
>> resource
>> using reference parameters should be carefully weighed against the
>> benefits of identifying a resource solely by URI as explained in  
>> [AoWWW,
>> Section 2.1] of the Web Architecture.
>> ]]
>> http://www.w3.org/TR/ws-addr-core/#resourceidentification
>> Noah Mendelsohn, from the TAG, mentioned WS-Naming as a bad example
>> during a workshop last February.
>> Regards,
>> Philippe
>>

Response:

1) The WS-Naming[1] Endpoint Identifier (EPI) is a URI, actually IRI.  
This is consistent with the Architecture of the World Wide Web,  
Volume One [2] Section 2, which recommends the use of URIs to  
identify resources.

2) One option provided by WS-Naming Section 4.3 mandates that the  
wsa:Address field (mapped to the [destination] when appearing in the  
message) possess the properties of an EPI, e.g. uniqueness in space  
and time WS-Naming Section 4.1. This is a stronger requirement than  
normally placed on the wsa:Address but strongly aligned with the  
goals of the AoWWW Section 2.2.

3) The presence of IRIs in both the wsa:Address and the EPI in the  
EPR amounts to the association of aliases for the resource. Aliases  
are indeed discouraged by the AoWWW Section 2.3.1, which reads.

"Although there are benefits (such as naming flexibility) to URI  
aliases, there are also costs. URI aliases are harmful when they  
divide the Web of related resources. A corollary of Metcalfe's  
Principle (the "network effect") is that the value of a given  
resource can be measured by the number and value of other resources  
in its network neighborhood, that is, the resources that link to it."

The impact on the "network effect" caused by the two aliases is  
mitigated by the explicit association of these aliases in the EPR.

Actually, the aim of WS Naming is to prevent the creation of multiple  
aliases of equal (heavy) weight. The EPI is intended as the single,  
persistent identifier of the resource. In WS Naming the wsa:Address  
is the (temporary) destination of a messages intended for the  
resource identified by the EPI. Use cases of the WS-Naming working  
group identify the unavoidable mobility of resources. The limitation  
that the wsa:Address of a resource is (in most general practice) both  
the identity and the message destination means that, in the presence  
of mobility, aliases are inevitable. It is one of the aims of WS- 
Naming to provide for persistent, unique identifiers for mobile  
resources.

4) Note that WS-Naming says nothing about the use of  
ReferenceParamenters for identification, a practice we discourage, as  
it splits the notion of identifier across two fields in the EPR.

I hope this clarifies the position of the WS-Naming working group.

[1] WS-Naming Public Comment Draft
http://www.ogf.org/Public_Comment_Docs/Documents/Jan-2007/draft-ogf- 
ws-naming-spec-006.pdf

[2] AoWWW
http://www.w3.org/TR/webarch/
or
http://www.w3.org/TR/2004/REC-webarch-20041215/


[3] WS-Addressing
http://www.w3.org/TR/ws-addr-core/
or
http://www.w3.org/TR/2006/REC-ws-addr-core-20060509/


-- 

Take care:

     Dr. David Snelling < David . Snelling . UK . Fujitsu . com >
     Fujitsu Laboratories of Europe Limited
     Hayes Park Central
     Hayes End Road
     Hayes, Middlesex  UB4 8FE
     Reg. No. 4153469

     +44-208-606-4649 (Office)
     +44-7768-807526  (Mobile)