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acknowledges the service owner that the service has been started. The
entity reference of the newly created service instance will be published via
a dictionary service and a naming service for customers to discover and
access the service.
To enable SLA management functionalities for a particular service, the
service owner needs to upload the model of the SLA Manager to SAP. The
model may follow a generic SLA Manager model or a modii ed version
based on a core model (e.g., an SLA-based service). Once the service is up
and running, a service client can access the external interfaces of SLA
Manager via the entity reference of the service. The service provider can
also send requests to the SAP for modifying the existing service model
or uploading a new model to the SAP. The model-based design gives the
service provider the l exibility to edit or modify the service model for
customization.
10.3.1.4
CIM Models of SLA Manager
In SSP, the models are described using the common information model
(CIM) meta-model. The models contain meta-information of the services
in a standardized construct format and are often described using MOF
[12]. The MOF i le describes the classes, associations, references, types,
methods, instance declarations, comments, and so on in textual format.
The CIM model of the SLA manager may include the operation models,
the data models, and, sometimes, the instance models in one or multiple
text-based MOF i les. An operation model dei nes the service type and
declares the service's external interfaces; a data model describes the data
structures of certain entities; and an instance model creates the instance of
certain entities and specii es the values of the instances.
The core of SLA Manager is the SLA-based service, which consists of the
operation model that describes SLA negotiation operations, and the data
model that dei nes the data structure, and several instance models for cre-
ating the SLA template instances. Once the models are uploaded to SAP,
SLA template instances will be created so as to allow service clients to
retrieve the SLA templates from the service provider. When a client
proposes an SLA, an instance of the SLA proposal will be created in the
SAP which contains the specii cations of the client's requirements. We
will describe the copy management of SLA proposals/agreements during
the negotiation processes described later in the chapter.
Figure 10.4
provides an example MOF i le of an SLA-based service for
basic SLA negotiation operations. For example, operation getSLATem-
plates() retrieves the SLA template instances from the SAP. The operation
proposeSLA() allows service client/provider to propose or counter-propose
an SLA by i lling in the detailed requirements in an SLA proposal instance.
As mentioned before, SLA Manager is one of the software modules
within a service entity. Besides SLA Manager, the service provider may
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