Diagrams created to represent attributes as well as entities and relationships may be called entity-attribute-relationship diagrams, rather than entity–relationship models.Īn ER model is typically implemented as a database. It can also be expressed in a verbal form, for example: one building may be divided into zero or more apartments, but one apartment can only be located in one building.Įntities may be characterized not only by relationships, but also by additional properties ( attributes), which include identifiers called "primary keys". It is usually drawn in a graphical form as boxes ( entities) that are connected by lines ( relationships) which express the associations and dependencies between entities. Typically, it represents records of entities and events monitored and directed by business processes, rather than the processes themselves.
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