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
|
Definition
| The process of defining a more general entity type from a set of more specialized entity types. BOTTOM-UP |
|
|
Term
|
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
|
Definition
| An attribute of the supertype whose values determine the target subtype(s) |
|
|
Term
|
Definition
| a simple attribute with alternative values to indicate the possible subtypes |
|
|
Term
|
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
|
Definition
| Set of one or more entity types and associated relationships grouped into a single abstract entity type |
|
|
Term
|
Definition
| are generic models that can be customized for a particular organization’s business rules |
|
|
Term
|
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
|
Definition
| rule expressing static structure. Includes attributes, relationships, and definitions |
|
|
Term
|
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
|
Definition
Controlling–something must or must not happen
Influencing–guideline for which a notification must occur |
|
|
Term
|
Definition
| an object on which actions are limited |
|
|
Term
|
Definition
| creation, deletion, update, or read |
|
|
Term
|
Definition
| an object influencing the ability to perform an action on another business rule |
|
|
Term
|
Definition
| A relation is a named, two-dimensional table of data |
|
|
Term
|
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
|
|
Term
|
Definition
| Allowable values for an attribute. |
|
|
Term
|
Definition
| No primary key attribute may be null. All primary key fields MUST have data |
|
|
Term
|
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
|
Definition
| don’t allow delete of “parent” side if related rows exist in “dependent” side |
|
|
Term
|
Definition
| automatically delete “dependent” side rows that correspond with the “parent” side row to be deleted |
|
|
Term
|
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
|
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 |
|
|
