Review of DB Models

1
Review of DB Models

• K.R. Riggs
• January 10, 2001

2
(some) Data Models

• model a way to specify the facts of interest
• Entity-Relation (ER)
• Relational (rel)
• Object Oriented (OO)
• KWEBS
• XML
• semi-structured data

3
Entity-Relationship Model

• Entity sets
• Attributes
• keys
• Relationships
• Edges
• arity 1-1, 1-n, m-n
• ISA
• PART-OF

Name Phone Salary EMPS AssignedTo Name
DEPTS Location Manages
MANAGERS Name
4
Relational Model
EMPS(EName, Phone, Salary) DEPTS(DName,
Location) MANAGERS(MName) AssignedTO(EName,DName)
Manages(EName,DName) Constraints EName
?AssignedTo? DName EName ?Manages? DName DName
?Manages? EName

• Relation (s)
• Attribute
• key
• foreign keys
• Constraints
• unique by key
• dependencies (semantics)

5
OO model

• Object (w/id other attributes)
• Complex Objects
• Type Hierarchy

OBJECT
EMP
DEPT Name,Phones,Salary,DEPT()
Name, Location DEPT()
MANAGER