After creating a Mediator component, you associate it with inbound service operations or event subscriptions and with outbound targets. Targets are outbound service operations or event publishing. A target specifies the next service or event to which a Mediator sends messages and also specifies which service operation to invoke. You can specify a service or an event as a target type.

You can also echo source messages back to the initial caller after any transformation, validations, assignments, or sequencing operations are performed. An echo can only be specified if the Mediator component has a synchronous or asynchronous interface. Whether the echo is synchronous or asynchronous depends on the WSDL file of the caller. The echo option is only available for inbound service operations and is not available for event subscriptions.

The purpose of the echo option is to expose all the Mediator functionality as a callable service without having to route it to any other service. For example, you can call a Mediator to perform a transformation, a validation, or an assignment, and then echo the Mediator back to your application without routing it anywhere else.

You can specify multiple routings for an inbound operation or event. Each routing is mapped to one target service invocation or event. Therefore, to specify multiple service invocations or raise multiple events, you must specify one routing rule for each target. For example, you can invoke an operation based on a message payload from the following operations defined in a service:

• insert

• update

• updateid

• delete

To do this action, you must create four routing rules, one for each operation. Later, when you specify a filter expression for each rule, you can specify which target and operation is applied to each message instance based on the message payload, as shown in Figure 20-3.