CSE 403: UML Class Diagram Design and Software Architecture

This document provides a comprehensive overview of UML class diagrams, essential for object-oriented software design. It covers the fundamental concepts, including the purpose of UML, the elements of a class diagram (classes, attributes, methods), and the relationships between classes (generalization, association, aggregation, composition, and dependency). The document also explains how to create UML diagrams, including visibility attributes and method parameters, and offers a practical design exercise using a Texas Hold'em poker game to illustrate the application of UML class diagrams in a real-world scenario. Furthermore, it discusses the pros and cons of using class diagrams in software design and includes references to tools for creating UML diagrams. This resource is valuable for students and professionals looking to understand and apply UML class diagrams effectively.

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Design and UML Class Diagrams
Suggested reading:
Practical UML: A hands on introduction for developer
http://dn.codegear.com/article/31863
UML Distilled Ch. 3, by M. Fowler

How do people
draw / write down
software architectures?

Example architectures
person
UW student
CSE 403
student
VerizonWireless
GPS satellite
Cell phone
sea agent
lake agent
amphibious
agent

Big questions
• What is UML?
– Why should I bother? Do people really use UML?
• What is a UML class diagram?
– What kind of information goes into it?
– How do I create it?
– When should I create it?

Design phase
• design: specifying the structure of how a software
system will be written and function, without actua
writing the complete implementation
• a transition from "what" the system must do, to
"how" the system will do it
– What classes will we need to implement a system that
meets our requirements?
– What fields and methods will each class have?
– How will the classes interact with each other?

How do we design classes?
• class identification from project spec / requirement
– nouns are potential classes, objects, fields
– verbs are potential methods or responsibilities of a clas
• CRC card exercises
– write down classes' names on index cards
– next to each class, list the following:
• responsibilities : problems to be solved; short verb phrases
• collaborators: other classes that are sent messages by this class
(asymmetric)
• UML diagrams
– class diagrams (today)
– sequence diagrams
– ...

What is UML?
• UML: pictures of an OO system
– programming languages are not abstract enough for O
design
– UML is an open standard; lots of companies use it
• What is legal UML?
– a descriptive language: rigid formal syntax (like
programming)
– a prescriptive language: shaped by usage and convention
– it's okay to omit things from UML diagrams if they aren
needed by team/supervisor/instructor

Uses for UML
• as a sketch: to communicate aspects of system
– forward design: doing UML before coding
– backward design: doing UML after coding as documentation
– often done on whiteboard or paper
– used to get rough selective ideas
• as a blueprint: a complete design to be implemented
– sometimes done with CASE (Computer-Aided Software
Engineering) tools
• as a programming language: with the right tools, code
be auto-generated and executed from UML
– only good if this is faster than coding in a "real" language

UML
In an effort to promote Object Oriented designs
three leading object oriented programming
researchers joined ranks to combine their
languages:
– Grady Booch (BOOCH)
– Jim Rumbaugh (OML: object modeling technique)
– Ivar Jacobsen (OOSE: object oriented software eng
and come up with an industry standard [mid 1990’s

UML – Unified Modeling Language
• Union of all Modeling Languages
– Use case diagrams
– Class diagrams
– Object diagrams
– Sequence diagrams
– Collaboration diagrams
– Statechart diagrams
– Activity diagrams
– Component diagrams
– Deployment diagrams
– ;.
• Very big, but a nice standard that has been
embraced by the industry.

Object diagram (≠ class diagram)
• individual objects (heap layout)
– objectName : type
– attribute = value
• lines show field
references
• Class diagram:
– summary of all possible object diagrams

Object diagram example