Data, Processes, and Events: Keys to Comprehensive Analysis - High-Performance Web Databases: Design, Development, and Deployment - page 63

Exhibit 4-16. Entity-event-relationship diagram for the order-entry system.
diagram that significantly bonds events to data and stage changes in enti-
ties is still needed. The structured event network shows the relationship of
events but is an unsatisfactory link to other diagrams.
Object-oriented analysis (OOA) has many useful diagrams. Object-Oriented
Analysis notations can be used to show the relationships of events to data
and other events in the EERD, which resembles an ERD. The boxes in the
EERD still represent data entities, and the lines represent relationships.
However, each data entity shows the stages it can enter.
Each entity can be thought of as a machine and each stage box as a but-
ton. Exhibit 16 is a partial EERD of the order entry system. It shows how
one entity's event can push another entity's button. The direction of the
arrows is important because it shows cause and effect. In addition, the
standard symbols to show triggers from input (i.e., a parallelogram) and
time (i.e., a box) have been added.
The diagram shows that the Pick event in ORDER triggers the Pickevent
in LINE ITEM. In turn, the Pick event in LINE ITEM causes the Allocate event