During the update call, the subject is initiating a callback to the observer; thus, at that point, the subject is the service requester and the observer is the service provider.
In web services terminology, the observer is initially the service requester and the subject is initially the service provider.
在Web服务术语中,最初观察者是服务请求者,目标是服务提供者。
3
For the requests coming into ESB flow from the trading system client, Business events is an external service, or more precisely, an observer detecting patterns of events without influencing the flow.