Entity types represent thing about which data is stored such as people, object, Location, or events. All the different diagrams and their objects are among the entity types. for example, data flow diagrams, processes, data store, data flows, and external entities, are all entity types. So are data model diagrams, data entities, and data relationships.
The XL repository data model defines 61 entity types. each is identified by a unique 3-character abbreviation. each entity type is described in detail in the excelerator windows data and reports reference guide. a summary of the entity types appears in appendix A.
Entity type are linked to other entity types in a variety of ways. These linkages are called relationship types. A relationship type is a combination of two entity types and a relation verb. For example, record contains element, is a relationship types, with entity types, record and element, and verb, contain. for each relationship. there is a reverse relationship, so in this case the reverse relationship verbs is provided in table 2.1, pages 26-28, of Excelerator windows data and reports reference guide.