Simple web services topology
In this topology WebSphere® Application Server is used solely as a notification broker to enable producing and consuming WS-Notification applications to communicate with each other. The applications are unaware that the NotificationBroker service is implemented by WebSphere Application Server.
In the following figure, the publisher, subscriber and notification consumer are connected to the notification broker by SOAP over HTTP. The publisher, subscriber and notification consumer are unaware that the broker is backed by WebSphere Application Server.

There are a variety of clients that are able to connect to the notification broker provided by WebSphere Application Server. Any web service client that implements or invokes the WS-Notification message exchanges can connect. This includes the various types of web service clients that are supported directly by WebSphere Application Server and other web service clients that are capable of using JAX-RPC or JAX-WS patterns (for example .NET). This is illustrated in the following diagram:

In a different topology, it is possible that none of the clients of the notification broker are written or hosted in a WebSphere Application Server environment. The notification broker itself cannot determine the environment from which the clients connect because the only interaction is through the standard web service exchanges defined by WS-Notification. This is shown in the following figure.

Similarly, WS-Notification applications written or hosted in a WebSphere Application Server environment (such as JAX-RPC from AppClient, JSR172, JSR101) can connect to non-IBM NotificationBrokers (or NotificationProducers) without any changes to the application code.