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Business Rule
A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business.
Term
A word or phrase that has a specific meaning for the business.
Fact
An association between two or more terms.
Entity
A person, a place, an object, an event, or a concept in the user environment about which the organization wishes to maintain data.
Entity type
A collection of entities that share common properties or characteristics.
Entity instance
A single occurrence of an entity type.
Strong entity type
An entity that exists independently of other entity types.
Weak entity type
An entity type whose existence depends on some other entity type.
Identifying owner
The entity type on which the weak entity type depends.
Identifying relationship
The relationship between a weak entity type and its owner.
Attribute
A property or characteristic of an entity or relationship type that is of interest to the organization.
Required attribute
An attribute that must have a value for every entity (or relationship) instance with which it is associated.
Optional attribute
An attribute that may not have a value for every entity (or relationship) instance with which it is associated.
Composite attribute
An attribute that has meaningful component parts (attributes).
Simple (or atomic) attribute
An attribute that cannot be broken down into smaller components that are meaningful to the organization.
Multivalued attribute
An attribute that may take on more than one value for a given entity (or relationship) instance.
Derived attribute
An attribute whose values can be calculated from related attribute values.
Identifier
An attribute (or combination of attributes) whose value distinguishes instances of an entity type.
Composite identifier
An identifier that consists of a composite attribute.
Relationship type
A meaningful association between (or among) entity types.
Relationship instance
An association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type.
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.
Degree
The number of entity types that participate in a relationship.
Unary relationship
A relationship between instances of a single entity type.
Binary relationship
A relationship between the instances of two entity types.
Ternary relationship
A simultaneous relationship among the instances of three entity types.
Cardinality constraint
A rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity.
Minimum cardinality
The minimum number of instances of one entity that may be associated with each instance of another entity.
Maximum cardinality
The maximum number of instances of one entity that may be associated with each instance of another entity.
Time stamp
A time value that is associated with a data value, often indicating when some event occurred that affected the data value.
Entity-Relationship Model
A logical representation of the data for an organization or for a business area, using entities for categories of data and relationships for associations between entities.
Entity-Relationship Diagram (ERD)
A graphical representation of an entity-relationship model.
