Event-driven analysis can add an extra degree of rigor to both data and functional modeling as well as to the process of systems analysis. This chapter introduces modeling tools that combine process, data, and event techniques. Entity-life history diagrams show all the events in the life of an entity; that is, all the states in which the entity can exist during its life. Each stage of life of an entity is represented by one or more functions in a process model. An important practice in analyzing life stages is that in addition to identifying the specific functionality required, analysts must also identify the events required to change the entity’s state. A relationship is considered full if the new occurrence of an entity immediately establishes a relationship with at least one occurrence of another entity. The practitioner must go through the same procedure using the LINE ITEM as the causal entity and ORDER as the affected entity.