Universal Modeling Language (UML) Class Diagrams Compared to EER

1
EER vs. UML Terminology
EER Diagram Entity Type Entity Attribute Domain Co
mposite Attribute Derived Attribute Relationsh
ip Type Relationship Instance Cardinality
Participation

• UML Class Diagram
• Class
• Object
• Attribute
• Domain
• Structured Domain
• Operation
• Association
• Link
• Multiplicities

2
EER Example
Department
Participation
1
N
Cardinality
Employee
N
Assigned To
M
Project
3
DiagramsEER vs. UML
Class
Attributes
Methods
Structured Domain
Entity Type vs. Class Attribute Composite
Attribute vs. Structured Domain
4
EER vs. UMLComplete Diagram
1..1
Min participation (0 or some int n ngt0)
0..
Department
1
Is In
N
Max Cardinality
N
0..
Assigned To
M
0..
Project
5
EER Derived Attributes - Include in Department
the average salary of the employees in the
department.
Employee
Department
Class Method
6
EERMulti-valuedAttributes

• EER Multi-valued
• as Entity

N
3
Student
Student
Major_Program
Major
UML
0..
0..3
7
Weak Entities
EER Weak Entity
8
Aggregations

Location
Location

Department
Project
No
No
Name
No
Name

Project Name No
0..
1..
1..1
0..
Location Name
9
Example University Database

• Superclasses Subclasses
• Generalization Specialization
• Inheritance

Employee
U
Person
Grad Student
U
U
Student
U
Superclass instance must always exist.
Undergrad Student
10
UML Superclass/SubclassInheritance
EER UML disjoint overlapping
11
Object-Oriented Approach Motivation

• Object-Oriented Databases (OODB)
• Add persistence to object-oriented programming
  languages

• Object Relational Databases (ORDBMS)
• Add user-defined methods to relational databases
• Allow grouping of relations into more complex
  objects

12
Relational is Good For

• Fixed format data
• Transaction processing
• simple short transactions
• Concurrency control
• Recovery from crashes
• Query processing and Query optimization
• relational algebra and mathematical logic
  operations.

13
Problems

• The relational model has no notion of a single
  object.
• Context with the real world
• e.g., spatial context.
• Aggregation functions may be desired
• The notion of re-use cannot be exploited
• There may also be versions or variant
  configurations
• i.e variations of the same design.

14
Problems With the Relational Model - 1

• Nonhomogeneous collection of design objects.
• Data Types images, matrices, vectors variable
  length.
• Temporal and/or spatial data.
• Many data types few instances of each type.

15
Problems With the Relational Model - 2

• Schemas evolve during design.
• Long running transactions "checkout a design".
• Versions design log.

16
Problems With the Relational Model - 3

• Functions needed
• Making a design permanent,
• Releasing design to production,
• Archiving design,
• etc.
• Library of design objects
• minimize redundancy.

17
Object-Oriented Concepts - 1

• Complex Objects
• sets,
• bags,
• lists,
• arrays,
• tuples.

18
Object-Oriented Concepts - 2

• Object Identity identify by object id (oid)
  rather than by an attribute value, never changes.
• Encapsulation Operations and Data available to
  user.
• Implementation hidden. No other operations
  available.

19
Object-Oriented Concepts - 3

• Types and/or Classes
• Type
• Interface and Implementation.
• Types declared, checked at compile-time
• Class
• Instances created at run-time

20
Object-Oriented Concepts - 4

• Class or Type Hierarchies
• Inheritance both data and function
• example student undergraduate, graduate
• Overriding, overloading, and late binding
• Polymorphism

21
Object-Oriented Concepts - 5

• Computational Completeness
• Extensibility
• Means to define new types.
• User types not distinguished from system types.
• Persistence
• Not present in OO programming languages.
• Should be implicit not explicit.

22
Object-Oriented Concepts - 6

• Secondary Storage Management
• Concurrency
• Recovery
• Ad Hoc Query Facility

23
Review Object

• State (value)
• Behavior (operations)
• Signature or interface operation name and
  arguments
• Method or body implementation
• Identified by unique Object Identifier (OID)

24
Class

• Group of similar objects
• Class hierarchies
• Inheritance
• Persistence must be specified explicitly
• Via entry point
• Via reachability

25
Type Hierarchies and Inheritance(EER
superclass/subclass relationship)
PERSON Name, Address, Birthdate, Age,
SSN EMPLOYEE subtype-of PERSON Salary,
HireDate, Seniority STUDENT subtype-of PERSON
Major, GPA EMPLOYEE Name, Address, Birthdate,
Age, SSN, Salary, HireDate, Seniority STUDENT
Name, Address, Birthdate, Age, SSN, Major, GPA
26
Object Data Management Group (ODMG)

• Object Model
• Object Definition Language (ODL)
• Object Query Language (OQL)
• Bindings to object-oriented programming languages
• C, Java, Smalltalk