Type I is the conventional one-way WS interaction pattern,where the client makes a one-way WS request to the server.
Type II is the interaction pattern of asynchronous reply and event notification from the server to the client. In practice, an
asynchronous reply is often modeled as event notification with some correlation information with which the client can
associate the reply to its request. The type II interaction pattern is separated into two sub-classes, depending on the response pattern. If the server solicits acknowledgement from the client when the client receives the event report from the server, then the Type II interaction pattern is called “solicitation.” If no acknowledgement is solicited after receiving the event report, then the Type II interaction pattern is called “notification.” Type III is the reversal of the Type I interaction pattern, where the server issues the service request to the client. The patterns of these interactions are illustrated in the Figure 3, where solid arrows indicate initial messages, and dotted arrows indicate optional response messages