The collection of all the entities important to the business, to which a specific definition and common predicates apply.
Most businesses have suppliers, deal with products, and sell them to customers. There are thus likely to be data about individual suppliers (e.g., Poly Leisure Products of Hong Kong). Poly Leisure Products is an entity; the collection of all suppliers is the SUPPLIER entity type. The collection of all customers is the CUSTOMER entity type. A sample customer entity may be Harrods Department Store.
Tangible Entity Type
An entity type whose entities are physical objects or particular views of physical objects.
Conceptual Entity Type
An entity type whose entities are intangible objects without physical form.
Associative Entity Type
An entity type whose entities relate to two or more entities. Associative entity types are used to resolve many-to-many relationship types in an entity relationship diagram. For example, each entity of the entity type CLUB MEMBERSHIP relates one entity of CLUB with one entity of MEMBERSHIP.
Collective Entity Type
An entity type whose entities gather together or consist of entities from one or more other types. In some cases, a collective entity type may be helpful in improving the performance of a system.
Component Entity Type
An entity type whose entities form part of a larger collective entity type.
Overlapping Entity Types
Two or more entity types with entities in common. Overlapping entity types are to be avoided.
Isolated Entity Type
An entity type that does not participate in any relationship.
Transient Entity Type
An entity type whose entities are of only short-term interest to the enterprise.
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