[NEW ISSUE] Number of messages needed to retrieve the content of a service group

["Murray, Bryan P." <bryan.murray@hp.com>]

Title: Number of messages needed to retrieve the content of a service
group

Description:

Section 5 of WS-SG says "The grouping and membership aspects of a 
ServiceGroup are only manifest in the linkage between a ServiceGroup 
and a ServiceGroupEntry". And section 5.1.2, in the description of 
/wsrf-sg:Entry/ServiceGroupEntryEPR says: "Endpoint reference as 
defined in [WS-Addressing] to the ServiceGroupEntry WS-Resource with 
which the entry is associated. This WS-Resource is the representation 
of the membership of the member in the group. Existence of this 
WS-Resource is the definitive test that the member is indeed part of 
the group. If the WS-Resource referenced by ServiceGroupEntryEPR is 
not available, the consumer MUST NOT assume that the Web service 
referenced by the @MemberServiceEPR is a member of the service group."

This means that in order to retrieve the membership of a 100-members 
service group, one has to send and receive 101 messages. One to retrieve
the resource properties doc of the group and one to each entry. This 
is a huge cost and basically means that service groups of more than a 
handful of members cannot be used (or only in a very limited way) if 
one obeys the spec.

Proposed resolution:

Remove the wording identified above and as a result make the content 
of the service group resource properties document the authoritative 
source of membership in the service group. Make Entry services 
optional, to be used when additional control on the membership (such 
as managing the lifecycle of the membership or registering for
notification)
is offered.