Design of a Model-Based SLA Management Service and Its Applications over Distributed SOA Environments - Grid Computing: Infrastructure, Service, and Applications - page 259

service provider may reject the SLA proposal, accept the proposal, or offer
a counter-proposal.

• Reject proposal: The service provider rejects the request by return-

ing an empty SLA proposal object to the client.
Accept proposal: • The service provider accepts the offer by provid-

ing additional information regarding the service such as service
price and end-point details. The service provider may attach its
digital signature agreeing to the proposal. At this stage, this SLA
becomes binding, once the client signs the SLA.
Offer counter-proposal:

• Sometimes, the service provider may not

agree with the terms offered by the customer. In this case, the
service provider may return a counter-offer that is different from
the original offer.

10.4.2.3 Agreeing/Disagreeing to SLA

The negotiation of an SLA may be terminated when any one of the follow-
ing scenarios happens:

• Both parties have signed the SLA proposal . When both the service

provider and the client add their digital signatures in the SLA
proposal, an SLA is considered to have been established. Hence,
the negotiation terminates.
Both or either one of the parties reject(s) the proposal

• . Both the parties

have the right to reject a proposal from its counter-part. In our
proposed SLA manager, the service client can reject the service
provider's SLA proposal by invoking the rejectSLA() function,
while the service provider can decline the client request by return-
ing an empty SLA proposal.
Negotiation time-out • . Either side can abandon the negotiation pro-

cess if the other party does not respond in time. The SLA negotiation
will automatically stop if there is no reply from the other party till
the required response deadline.

Once an SLA has been established, the service provider will provide the
service to the client under the terms of the SLA.

10.4.2.4 SLA Lifecycle

Figure 10.6 describes the lifecycle of an SLA. When an SLA is i rst created
based on an SLATemplate, the SLA proposal is in pending state. At this
state, the proposal is ready to be submitted to the service provider. Once
the proposal is submitted, it enters the proposed state. When both the ser-
vice provider and the client agree on the SLA proposal by adding their