Data Modeling Flashcards
A good business rule is:
(1) declarative
(2) precise
(3) atomic
(4) consistent
(5) expressible
(6) distinct
(7) business-oriented
A good data name is:
(1) related to business
(2) meaningful and self-documenting
(3) unique
(4) readable
(5) composed of words from an approved list
(6) repeatable
A logical representation of the data from an organization or for a business area, using entities for categories of data and relationships for associations between entities
ENTITY-RELATIONSHIP MODEL
A graphical representation of an entity-relationship model
ENTITY-RELATIONSHIP DIAGRAM
A person, a place, an object, an event, or a concept in the user environment about which the organization wishes to maintain data
ENTITIES
Person, place, object, event, concept (corresponds to a row in a table)
ENTITY INSTANCE
Collection of entities (corresponds to a table)
ENTITY TYPE
Link between entities
RELATIONSHIP INSTANCE
Category of relationship, link between entity types
RELATIONSHIP TYPE
Property or characteristic of an entity or relationship type
ATTRIBUTE
Often corresponds to a field in a table
ATTRIBUTE
Entity is an object that will have many instances in the database.
TRUE
Entity is an object that will be composed of multiple attributes. T or F?
TRUE
Entity is an object that we are trying to model
TRUE
Entity is a user of the database system
FALSE
Entity is an output of the database system.
FALSE
Property or characteristic of an entity or relationship type
ATTRIBUTE
An attribute that has meaningful component parts
COMPOSITE ATTRIBUTE
An attribute that cannot be broken down into smaller components that are meaningful to the organization
SIMPLE (OR ATOMIC) ATTRIBUTE
An attribute that may take on more than one value for a given entity (or relationship instance)
MULTIVALUED ATTRIBUTE
An attribute whose values can be calculated from related attribute values
DERIVED ATTRIBUTE
An attribute (or a combination of attributes) that uniquely identifies individual instances of an entity type
IDENTIFIER (KEY)
An attribute that could be a key, satisfies the requirements for being an identifier
CANDIDATE IDENTIFIER
This relationship exist between tables when only one record of the first table is related to only one record on the second table
ONE-TO-ONE RELATIONSHIP
This relationship exist between tables when one record of the first table can be related to one or more records to a second table
ONE-TO-MANY RELATIONSHIP
This relationship exists between tables when one record of the first table can be related to one or more records to a second table or vice versa
MANY-TO-MANY RELATIONSHIP
Relationships are the glue that holds together the various components of an E-R model
MODELING RELATIONSHIPS
A meaningful association between (or among) entity types
RELATIONSHIP TYPE
An association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type
RELATIONSHIP INSTANCE
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
ASSOCIATIVE ENTITY
How do you know whether to convert a relationship to an associative entity type?
- All the relationships for the participating entity types are “many” relationships
- The resulting associative entity type has independent meaning to end users and, preferably, can be identified with a single-attribute identifier
- The associative entity has one or more attributes in addition to the identifier
- The associative entity participates in one or more relationships independent of the entities related in the associated relationship
The number of entity types that participate in that relationship
DEGREE OF RELATIONSHIP
Relationship between the instances of a single entity type
UNARY RELATIONSHIP
Relationship between the instances of two entity types.
The most common type of relationship encountered in data
BINARY RELATIONSHIP
Simulataneous relationship among instances of three entity types
TERNARY RELATIONSHIP
Recursive relationships
UNARY RELATIONSHIP
A rule that specifies the number of instances of one entity that can be associated with each instance of another entity
CARDINALITY CONSTRAINT
The minimum number of instances of one entity that may be associated with each instance of another entity
MINIMUM CARDINALITY
The maximum number of instances of one entity that may be associated with each instance of another entity
MAXIMUM CARDINALITY