Mediator provides several important capabilities to your SOA system.

The virtualization of Web services provides the following capabilities:

Loose coupling between service consumers and service providers enables greater flexibility in your SOA system. Loose coupling provides independence of location, protocol, and format between the consumers and providers. This means that changes made by either a consumer or a provider do not necessarily require a change in the other. This is because there is no direct connection between the two; instead, they depend upon Mediator for the connection. The Web service that the consumer invokes is hidden from the consumer application with Mediator serving as the mediation layer.

Because virtual services are created on CentraSite and deployed to Mediator, communication between the two is vital. CentraSite must communicate any virtual service updates to Mediator. CentraSite uses the target endpoint you register when you specify the target (Mediator) to automatically communicate changes in the virtual services to the instance of Mediator to which it is deployed.

Similarly, Mediator relies on CentraSite for any updates to the consumer applications that are authorized to access the virtual services.

Mediator enables you to report run-time events and performance metrics to CentraSite for all virtual services that are deployed to Mediator. You can view these events and performance metrics in CentraSite and configure your policies to send alerts when some kinds of events occur. For more information, see The Key Performance Indicator (KPI) Metrics.

You can optionally configure a virtual service if you need to transform the service request and response messages to suit your special needs. To do this, you can specify an XSLT file to transform the messages during the mediation process.

In addition, you can optionally configure virtual services to invoke Integration Server services to pre-process or post-process the request or response messages. All procedures for creating virtual services appear in the CentraSite documentation.

The policies you create for virtual services provide run-time governance capabilities for the virtual services. Similarly, the policy enforcement rules you create for virtualized APIs provide run-time governance capabilities for the APIs. Mediator provides built-in run-time actions that you can include in a policy or policy enforcement rule and then configure their parameters to suit your needs. These actions perform activities such as identifying or authenticating consumers, validating digital signatures, and capturing performance measurements.

There are two separate sets of built-in run-time actions you can use:

For more information, see Summary of the Built-In Run-Time Actions.

Mediator maintains a list of consumer applications specified in CentraSite that are authorized to access the virtual services deployed to Mediator. Mediator synchronizes this list of consumer applications through a manual process initiated from CentraSite.

Mediator hosts the virtual services that you create in CentraSite. Part of defining virtual services is configuring the policies that Mediator will enforce and the consumer applications that Mediator will monitor. When you deploy virtual services to Mediator, and service consumers make requests of the service provider, Mediator mediates and enforces the policies defined for the virtual service. Mediator then reports the collected events and performance metrics to CentraSite.

Multiple instances of Mediator can be clustered together to provide scalability of mediation. A load balancer can be placed in front of the clustered Mediator instances to properly distribute the request messages. For more information about load balancing, see Overview of Clustering and Load Balancing.