Each perspective, the Business Perspective for example, defines a horizontal or system-wide view of the architecture captured from four aspects: Data (what), Activity (how), Location (where), and People (who). The combination of these aspects completely defines the architecture from that perspective, provided that business rules (why) and business events (when) are also defined within the Activity viewpoint. This figure illustrates how, for example, the “Business Entities” viewpoint lens conceptually captures the IT architecture information for the viewpoint.