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C++ Data Structures
N/A
43
Computer Science
Undergraduate 3
06/05/2010

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Term
Subtype entities inherit ____________ of the supertype
An instance of a subtype is ____________ of the supertype
Definition
values of all attributes
also an instance
Term
Generalization:
Definition
The process of defining a more general entity type from a set of more specialized entity types. BOTTOM-UP
Term
Specialization:
Definition
The process of defining one or more subtypes of the supertype and forming supertype/subtype relationships. TOP-DOWN
Term
Completeness Constraints:
Definition
Whether an instance of a supertype must also be a member of at least one subtype
Total Specialization Rule: Yes (double line)
Partial Specialization Rule: No (single line)
Term
Disjointness Constraints:
Definition
Whether an instance of a supertype may simultaneously be a member of two (or more) subtypes
Term
Disjoint Rule:
Overlap Rule:
Definition
An instance of the supertype can be only ONE of the subtypes
An instance of the supertype could be more than one of the subtypes
Term
Subtype Discriminator:
Definition
An attribute of the supertype whose values determine the target subtype(s)
Term
Disjoint –
Definition
a simple attribute with alternative values to indicate the possible subtypes
Term
Overlapping –
Definition
a composite attribute whose subparts pertain to different subtypes. Each subpart contains a boolean value to indicate whether or not the instance belongs to the associated subtype
Term
Entity cluster:
Definition
Set of one or more entity types and associated relationships grouped into a single abstract entity type
Term
Packaged data models
Definition
are generic models that can be customized for a particular organization’s business rules
Term
Business Rules
Definition
Statements that define or constrain some aspect of the business
Term
3 classificatins of business rules
Definition
Classification of business rules:
Derivation
Structural assertion
Action assertion
Term
Classification of business rules:
Derivation–
Definition
rule derived from other knowledge, often in the form of a formula using attribute values
Term
Structural assertion–
Definition
rule expressing static structure. Includes attributes, relationships, and definitions
Term
Action assertion–
Definition
rule expressing constraints/control of organizational actions
Term
Types of Action Assertions:
Result
Definition
Condition–IF/THEN rule
Integrity constraint–must always be true
Authorization–privilege statement
Term
Types of Action Assertions:
Form
Definition
Enabler–leads to creation of new object
Timer–allows or disallows an action
Executive–executes one or more actions
Term
Rigor
Definition
Controlling–something must or must not happen
Influencing–guideline for which a notification must occur
Term
Anchor Object–
Definition
an object on which actions are limited
Term
Action–
Definition
creation, deletion, update, or read
Term
Corresponding Objects–
Definition
an object influencing the ability to perform an action on another business rule
Term
Relation
Definition
A relation is a named, two-dimensional table of data
Term
Table
Definition
Table consists of rows (records) and columns (attribute or field)
Term
Requirements for a table to qualify as a relation:
Definition
It must have a unique name
Every attribute value must be atomic (not multivalued, not composite)
Every row must be unique (can’t have two rows with exactly the same values for all their fields)
Attributes (columns) in tables must have unique names
The order of the columns must be irrelevant
The order of the rows must be irrelevant
Term
Correspondance of relational model with ER Diagram
Definition
Relations (tables) correspond with entity types and with many-to-many relationship types
Rows correspond with entity instances and with many-to-many relationship instances
Columns correspond with attributes
Term
Primary Keys and Foreign keys
Definition
Primary keys are unique identifiers of the relation in question. Examples include employee numbers, social security numbers, etc. This is how we can guarantee that all rows are unique
Foreign keys are identifiers that enable a dependent relation (on the many side of a relationship) to refer to its parent relation (on the one side of the relationship)
Term
Keys can be ___(a single field) or ___(more than one field)
Definition
simple, composite
Term
Domain Constraints
Definition
Allowable values for an attribute.
Term
Entity Integrity
Definition
No primary key attribute may be null. All primary key fields MUST have data
Term
Referential Integrity–
Definition
rule states that any foreign key value (on the relation of the many side) MUST match a primary key value in the relation of the one side. (Or the foreign key can be null)
Term
Delete Rules
Restrict–
Definition
don’t allow delete of “parent” side if related rows exist in “dependent” side
Term
Delete Rules
Cascade–
Definition
automatically delete “dependent” side rows that correspond with the “parent” side row to be deleted
Term
Set-to-Null–
Definition
set the foreign key in the dependent side to null if deleting from the parent side. Not allowed for weak entities
Term
Mapping Regular Entities to Relations
Simple attributes:
Composite attributes:
Multivalued Attribute:
Definition
E-R attributes map directly onto the relation
Use only their simple, component attributes
Becomes a separate relation with a foreign key taken from the superior entity
Term
Mapping Weak Entities

Primary key composed of:
Definition
Becomes a separate relation with a foreign key taken from the superior entity

Partial identifier of weak entity
Primary key of identifying relation (strong entity)
Term
Mapping Binary Relationships
One-to-Many–
Definition
Mapping Binary Relationships
One-to-Many–Primary key on the one side becomes a foreign key on the many side
Term
Mapping Binary Relationships
Many-to-Many–
Definition
Many-to-Many–Create a new relation with the primary keys of the two entities as its primary key
Term
Mapping Binary Relationships
One-to-One–
Definition
Primary key on the mandatory side becomes a foreign key on the optional side
Term
Mapping Associative Entities
Identifier Not Assigned
Definition
Default primary key for the association relation is composed of the primary keys of the two entities (as in M:N relationship)
Term
Mapping Associative Entities
Identifier Assigned
Definition
It is natural and familiar to end-users
Default identifier may not be unique
Term
AN ENTITY SHOULD NOT BE:
Definition
A user of the database system
An output of the database system (e.g., a report)
Term
Attributes of the identifier
Definition
Will not change in value
Will not be null
No intelligent identifiers (e.g., containing locations or people that might change)
Substitute new, simple keys for long, composite keys
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