Chapter 9. Extending the mediation 317
With this second group of mediation primitives, many improvements are achieved
such as implementing flows based on policy enforcement or more flexibility when
querying the WSRR for endpoints or SLAs.
9.2.1 Benefits of the SLA Endpoint Lookup primitive
The SLA Endpoint Lookup primitive is an improvement of the Endpoint Lookup
primitive. It combines into a single primitive the benefits described in 8.2.1,
“Benefits of a dynamic endpoint lookup in a mediation” on page 255 and in 8.2.2,
“Benefits of an SLA check in a mediation” on page 256. Using this primitive, the
mediation flow is easier to implement and understand. In addition, performance
can be improved because there is only one interaction between the mediation
module (WebSphere ESB) and the registry.
This primitive also provides a customization mechanism, so that the behavior of
the primitive can be adapted to support additional filters or even a different
WSRR information model.
9.2.2 Benefits of the Policy Resolution primitive
Mediation policies provide the ability achieve greater levels of flexibility and
administrative control over the mediation’s implementation, without changing the
actual implementation itself. You can control service interactions dynamically,
using context information.
Using mediation policies, the mediation flow dynamically configures service
interactions and primitives. At run time, the values of module properties that are
hard-coded in a mediation flow are replaced with the values that are defined in
the mediation policy that matches a given selection criteria. This selection criteria
can be based on the execution context or on the message content. Classification
systems, such us the life cycle status, can also be used as part of the selection
criteria.

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