Database Management: Chapter 2

Distinct

Business rules are not redundant, but a business rule may refer to to other rules (especially to definitions)

Business rules

Declarative Precise Atomic Consistent Expressible Distinct Business-oriented

Degree

The number of entity types that participate in a relationship

Precise

With the related organization, the rule must have only one interpretation among all interested people, and its meaning must be clear.

Declarative

a business rule is a statement of policy, not how policy is enforced or conducted; the rule does not describe a process or implementation, but rather describes what a process validates

Buiness-oriented

a business rule is stated in terms business people can understand, and because it is a statement of business policy, only business people can modify or invalidate a rule; thus, a business rule is owned by the business.

Atomic

a business rule marks one statement, not several; no part of the rule can stand on its own as a rule(that is, the rule is indivisible, yet sufficient.)

Expressible

a business rule must be able to be stated in natural language, but it will be stated in a structured natural language so that there is no misinterpretation

Consistent

a business rule must be internally consistent (that is, not contain conflicting statements) and must be consistent with ( and not contradict) other rules.

Entity type

a collection of entities that share common properties or characteristics

Entity-relationship diagram (ER diagram,ERD)

a graphical representation of an entity-relationship model

Entity-relationship model (ER model)

a logical representation of the data for an organization or for a a business area, using entities for categories of data and relationships for associations between entities

Relationship type

a meaningful association between (or among) entity types

Entity

a person, a place, an object, an event, or a concept in the user enviornment about which the organization wishes to maintain data

Attribute

a property or characteristic of an entity or relationship type that is of interest to the organization.

Unary relationship

a relationship between instances of a single entity type.

Binary relationship

a relationship between the instances of two 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

Ternary

a simultaneous relationship among the instances of three entity types.

Entity instance

a single occurence of an entity type

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

Time stamp

a time value that is associated with a data value, often indicating when some event occurred that affected the data value.

Term

a word or phrase that has a specific meaning for the business

Relationship instance

an association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type.

Fact

an association between two or more items

Identifier

an attribute (or combination of attributes) whose value distinguishes instances of an entity type.

Simple (or atomic) attribute

an attribute that cannot be broken down into smaller components that are meaningful to the organization

Composite attribute

an attribute that has meaningful component parts (attributes)

Optional attribute

an attribute that may not have a value for every entity (or relationship) instance with which it is associated

Multivalued attribute

an attribute that may take on more than one value for a given entity (or relationship) instance

Required attribute

an attribute that must have a value for every entity (or relationship) instance with which it is associated.

Derived attribute

an attribute whose values can be calculated from related attribute values

Strong entity type

an entity that exists independently of other entity types

Associate 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.

Weak entity type

an entity type whose existence depends on some other entity type

Composite identifier

an identifier that consists of a composite attribute

Identifying owner

the entity type on which the weak entity type depends

Maximum cardinality

the maximum number of instances of one entity that may associated with each instance of another entity.

Minimum cardinality

the minimum number of instances of one entity that may be associated with instance of another entity

Identifying relationship

the relationship between a weak entity type and its owner.