MIS 372 - Ch. 3
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MIS 372 - Ch. 3
MIS Modern Database Management 9th Edition
MIS Modern Database Management - 9th Edition
What is a 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.
What is the job of a Database Analyst?
Identify and understand those rules that govern data.
Represent those rules so that they can be unambiguously understood by information systems developers and users.
Implement thos rules in database technology.
A word or phrase that has a specific meaning for the business.
An association between two or more terms.
When should a data object be added to a data model?
Not until it has been carefully defined and named and there is agreement on this definition.
What is an 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.
What is an entity-relationship diagram?
A graphical representation of an entity-relationship model.
A person, place, object, event, or concept in the user environment about which the organization wishes to maintain data.
Define "entity type"
A collection of entities that share common properties or characteristics.
Define "entity instance"
A single occurrence of an entity type.
Define "strong entity type"
An entity that exists independently of other entity types.
Examples include STUDENT, EMPLOYEE, AUTOMOBILE, and COURSE.
Define "weak entity type"
An entity type whose existence depends on some other entity type.
Define "identifying owner (owner)"
The entity type on which the weak entity type depends.
Define "identifying relationship"
The relationship between a weak entity type and its owner.
A property or characteristic of an entity or relationship type that is of interest to the organization.
Define "required attribute"
An attribute that must have a value for every entity (or relationship) instance with which it is associated.
Define "Optional Attribute"
An attribute that may not have a value for every entity (or relationship) instance with which it is associated.
Define "Composite attribute"
An attribute that has meaningful component parts (attributes).
Define "Simple (or atomic) attribute"
An attribute that cannot be broken down into smaller components that are meaningful to the organization.
Define "Multivalued attribute"
An attribute that may take on more than one value for a given entity (or relationship) instance.
Define "Derived attribute"
An attribute whose values can be calculated from related attribute values.
An attribute (or combination of attributes) whose value distinguishes instances of an entity type.
Define "Composite Identifier"
An identifier that consists of a composite attribute.
Define "Relationship Type"
A meaningful association between (or among) entity types.
Define "Relationship instance"
An association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type.
Define "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.
The number of entity types that participate in a relationship.
Define "Unary Relationship"
A relationship between instances of a single entity type.
Define "Binary Relationship"
A relationship between the instances of two entity types.
Define "Ternary Relationship"
A simulataneous relationship among the instances of three entity types.
Define "Cardinality Constraint"
"Specifies the number of instances of one entity that can (or must) be associated with each instance of another entity.
Define "Minimum Cardinality"
The minimum number of instances of one entity that may be associated with each instance of another entity.
Define "Maximum Cardinality"
The maximum number of instances of one entity that may be associated with each instance of another entity.
Define "Time Stamp"
A time value that is associated with a data value, often indicating when some event occurred that affected the data value.