Chapter Ten

Associative entity An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances. Also called a gerund.
Attribute A named property or characteristic of an entity that is of interest to the organization. See also Multivalued attribute.
Binary relationship A relationship between instances of two entity types. This is the most common type of relationship encountered in data modeling.
Business rules Specifications that preserve the integrity of a conceptual or logical data model.
Candidate key An attribute (or combination of attributes) that uniquely identifies each instance of an entity type. See also Identifier, Primary key.
Cardinality The number of instances of entity B that can (or must) be associated with each instance of entity A. )
Conceptual data model A detailed model that captures the overall structure of organizational data while being independent of any database management system or other implementation considerations. See also Entity-relationship data model, Logical data model.
Degree The number of entity types that participate in a relationship.
Domain The set of all data types and values that an attribute can assume.
Entity instance (instance) A single occurrence of an entity type.
Entity-relationship data model (E-R model) A detailed, logical representation of the entities, associations, and data elements for an organization or business area.
Entity-relationshipĘdiagramĘ(E-RĘdiagram) A graphical representation of an E-R model.
Entity type A collection of entities that share common properties or characteristics.
Identifier A candidate key that has been selected as the unique, identifying characteristic for an entity type. See also Candidate key, Primary key.
Multivalued attribute An attribute that may take on more than one value for each entity instance.
Primary key See Identifier.
Relationship An association between the instances of one or more entity types that is of interest to the organization. See also Instance connection.
Repeating group A set of two or more multivalued attributes that are logically related.
Ternary relationship A simultaneous relationship among instances of three entity types.
Triggering operation (trigger) An assertion or rule that governs the validity of data manipulation operations such as insert, update, and delete.)
Unary relationship (recursive relationship) A relationship between the instances of one entity type.

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