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Modern Database Management Ch. 2
N/A
32
Computer Science
Graduate
03/02/2014

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Term
entity relationship (E-R) model
Definition
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
Term
entity-relationship (E-R) diagram
Definition
a graphical representation of an entity relationship model
Term
business rule
Definition
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
term
Definition
a word or phrase that has a specific meaning for the business
Term
fact
Definition
an association between two or more terms
Term
entity
Definition
a person place or object or event or concept in the user environment about which the organization wishes to maintain data
Term
entity type
Definition
a collection of entities that share common properties or characteristics (versus an entity instance); entity type is described just once with metadata in a database
Term
entity instance
Definition
a single occurrence of an entity type; many instances of an entity type may be represented by data stored in the database
Term
strong entity type
Definition
a entity that exists independently of other entity types
Term
weak entity type
Definition
an entity type whose existence depends on some other entity type
Term
identifying owner
Definition
an entity type on which the weak entity type depends
Term
identifying relationship
Definition
the relationship between a weak entity type and its owner
Term
attribute
Definition
a property or characteristic of an entity or relationship type that is of interest to the organization
Term
required attribute
Definition
an attribute that must have a value for every entity (or relationship) instance with which it is associated
Term
optional attribute
Definition
a attribute that may not have a value for every entity (or relationship) instance with which it is associated
Term
composite attribute
Definition
an attribute that has meaningful component parts (attributes)
Term
simple (or atomic) attribute
Definition
an attribute that cannot be broken down into smaller components that are meaningful to the organization
Term
multivalued attribute
Definition
an attribute that may take on more than one value for a given entity (or relationship) instance [e.g. skill]
Term
derived attribute
Definition
an attribute whose values can be calculated from related attribute values; [e.g. GPA]; should be avoided if possible, as it may become outdated
Term
identifier
Definition
an attribute (or combination of attributes) whose value distinguishes instances of an entity type (will brome primary key)
Term
composite identifier
Definition
an identifier that consists of a composite attribute
Term
relationship type
Definition
meaningful association between (or among) entity types; denoted by a line labeled with the name of the relationship
Term
relationship instance
Definition
an association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type
Term
associative entity
Definition
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
Term
degree
Definition
the number of entity types that participate in a relationship
Term
unary relationship
Definition
a relationship between instances of a single entity type
Term
binary relationship
Definition
a relationship between the instances of two entity types; most common
Term
ternary relationship
Definition
a simultaneous relationship among the instances of three entity types
Term
cardinality constraint
Definition
a rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity
Term
minimum cardinality
Definition
minimum number of instances of one entity that may be associated with each instance of another entity
Term
maximum cardinality
Definition
maximum number of instances of one entity that may be associated with each instance of another entity
Term
time stamp
Definition
a time value that is associated with a data value, often indicating when some event occurred that affected the data value
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