Universal Modeling Language (UML) Class Diagrams

EER vs. UML
Terminology
EER Diagram
Entity Type
Entity
Attribute
Domain
Composite Attribute
~ [Derived Attribute]
Relationship Type
Relationship Instance
Cardinality & Participation
UML
•
•
•
•
•
•
•
•
•
•
UML Class Diagram
Class
Object
Attribute
Domain
Structured Domain
Operation
Association
Link
Multiplicities
1
EER Example
E#
N
Is
In
1
D#
Department
DNAME
Employee
N
NAME
FNAME
Assigned
To
M
Project
LNAME
%TIME
UML
P#
PNAME
2
Diagrams
EER vs. UML
Class
E#
Employee
Employee
NAME
FNAME
Structured
Domain
E#
NAME: NameDom
FNAME
LNAME
Attributes
Methods
…
LNAME
Entity Type vs. Class
Attribute
Composite Attribute vs. Structured Domain
UML
3
Department
D#
DNAME
EER vs. UML
Complete Diagram
…
1..1
Min participation (0
or some int n: n>0)
D#
E#
N
Employee
Department
1
Is
In
DNAME
Max Cardinality
Employee
NAME
N
P#
Assigned
To
LNAME
…
0..*
AssignedTo
%TIME
Project
P#
PNAME
%TIME
PNAME
UML
E#
NAME: NameDom
FNAME
LNAME
0..*
M
Project
FNAME
0..*
…
4
EER Derived Attributes - Include in
Department the average salary of the
employees in the department.
Employee
Member
Of
Salary
Class
Method
Department
AvgSal
Department
D#
DNAME
AvgSal
UML
5
EER
Multi-valued
Attributes
Student
Major
EER Multi-valued
as Entity
Major
Student
N
Has
Major
3
Major_Program
UML
Student
…
…
UML
0..*
Major_Program
0..3 Major
…
6
Weak Entities
EER Weak Entity
Employee
Name
1
Dependent
Name
SSN
Employee
SSN
Name
…
Dependent
Name
UML
Dependents
Of
N
UML
Qualified Association
Dependent
…
…
7
Aggregations
Location
Location
Department
Project
Name
Project
Name 0..*
No
…
UML
No
No
Name
1..1 Location
Name
1..*
0..*
Department
Name
No
…
…
8
Example: University Database
EmpID
SSN
Person
Salary
d
disjoint
o
overlap
total
U
• Superclasses & Subclasses
• Generalization & Specialization
• Inheritance
superclass
Employee
partial
subclass
Degree
Program
o
Grad Student
Name
Student
Superclass instance
must always exist.
Major
Dept
d
Undergrad Student
Class
UML
9
UML Superclass/Subclass
Inheritance
EER UML
Employee
EmpID
Salary
…
Person
SSN
Name
…
Student
MajorDept
…
UML
disjoint
d
overlapping
o
GradStudent
DegreeProgram
…
UndergradStudent
Class
…
10
Object-Oriented Approach
Motivation
• Object-Oriented
Databases (OODB)
– Add persistence to
object-oriented
programming
languages
UML
• Object Relational
Databases (ORDBMS)
– Add user-defined
methods to relational
databases
– Allow grouping of
relations into more
complex “objects”
11
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.
UML
12
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
UML
i.e variations of the same design.
13
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.
UML
14
Problems With the Relational
Model - 2
• Schemas evolve during design.
• Long running transactions: "checkout a
design".
• Versions; design log.
UML
15
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.
UML
16
Object-Oriented Concepts - 1
• Complex Objects:
– sets,
– bags,
– lists,
– arrays,
– tuples.
UML
17
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.
UML
18
Object-Oriented Concepts - 3
• Types and/or Classes:
– Type:
• Interface and Implementation.
• Types declared, checked at compile-time
– Class:
• Instances created at run-time
UML
19
Object-Oriented Concepts - 4
• Class or Type Hierarchies:
– Inheritance: both data and function
example: student: undergraduate, graduate
• Overriding, overloading, and late binding:
– Polymorphism
UML
20
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.
UML
21
Object-Oriented Concepts - 6
• Secondary Storage Management:
• Concurrency:
• Recovery:
• Ad Hoc Query Facility:
UML
22
Review: Object
• State (value)
• Behavior (operations)
– Signature or interface: operation name and
arguments
– Method or body: implementation
• Identified by unique Object Identifier (OID)
UML
23
Class
• Group of similar objects
• Class hierarchies
– Inheritance
• Persistence must be specified explicitly
– Via entry point
– Via reachability
UML
24
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
UML
25
Object Data Management Group
(ODMG)
•
•
•
•
Object Model
Object Definition Language (ODL)
Object Query Language (OQL)
Bindings to object-oriented programming
languages
– C++, Java, Smalltalk
UML
26

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