Figure 3 shows some high level business process events like market search and negotiate. They could be created either by a business workflow engine or manually. They signify steps in various business processes, and they depend upon lower level application events in order to complete those steps. So, the process step events depend upon various events happening at the applications level. And so on. Figure 3 shows some of the dependencies as red arrows. The lower level events have to happen in order for the higher level events to happen. In fact, if the lower level events don’t happen, say because there’s a middleware error, the higher level events don’t happen either. And the transaction hangs up.
Consequently, when those lower level events do happen, they cause the higher level event that depends upon them to happen also. This is shown in figure 4 by the blue arrows. A higher level event is called complex because it is caused by many events, in fact a pattern of lower level events.
The highest level event in figure 4 is a summary (or view) of the progress of a transaction. Usually that event won’t happen at all unless there’s a special tool that tracks process events and creates views. The tool uses CEP techniques to detect patterns of process events and create a higher level view event that contains a summary of the process steps thus far. A transaction view is an event that is caused by steps in one or more business processes.
A view of the progress of a business transaction is quite a complex event, depending upon lots of process steps. It is an aggregation of process events over a time period. Funnily enough, although it is complex in the sense that it is aggregated from many other events, it is easier to understand than the cloud of lower level process events. It abstracts essential data from those lower level events, and omits unnecessary details.