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Subject: Issue: ServiceGroupEntry as a WS-Resource is too Heavyweight.
Issue: ServiceGroupEntry as a WS-Resource is too Heavyweight. The ServiceGroupEntry is a WS-Resource with lifetime, RPs, and an associated EPR. Except for the lifetime information, all information associated with it is duplicated in the Entry RPs of the ServiceGroup itself. Lifetime MAY also be included in both places, but this is not mandated. This duplication creates confusing semantics with respect to the coherency of the duplicates. Furthermore, an EPR is stored in the Entry, returned from the add operation, and used by the ServiceGroup and clients to reference the ServiceGroupEntry (e.g. for driving a destroy operation to remove the service from the group). EPRs however do not possess rich enough semantics to serve this function. In particular, they are not resilient. What is needed is a reliable 'key' to the Entry. In OGSI this was provided by the GirdServiceHandel, which had stronger semantics than EPRs. Specifications: - Service Groups Notes: Proposed Recommendations: The recommendation is that the ServiceGroupEntry be removed from the ServiceGroup model. The implications of this are: 1) The Entry may need to include it's key as either an element or an attribute. I'm not convinced that this is required. 2) The add operation will need to return a 'key' (URI?) that has the adequate properties that would allow a client to remove the entry. We will also need to include a remove operation to replace destruction of the ServiceGroupEntry. 3) We need to decide what to do about lifetime support for membership in a ServiceGroup, the function performed by the ServiceGroupEntry's lifetime capability. Options include: 2a) Ignore the issue and let it be a property of implementations that extend SG. 2b) Provide an (optional) lifetime element within the Entry RP, e.g. <MembershipExpires> xsd:dateTime </MembershipExpires>. In this later case, SGs have a uniform way to advertise the lifetime of its members membership status in the group (note this is not the lifetime of the service itself). However, the Registration interface will need an operation to manage the lifetime of the Entry, e.g. setMembershipExpriyTime (key, time). Status: Proposed Contact: David Snelling Cross Reference: None -- Take care: Dr. David Snelling < David . Snelling . UK . Fujitsu . com > Fujitsu Laboratories of Europe Hayes Park Central Hayes End Road Hayes, Middlesex UB4 8FE +44-208-606-4649 (Office) +44-208-606-4539 (Fax) +44-7768-807526 (Mobile)
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