Object-Oriented Software Design and Software Processes Hans - - PowerPoint PPT Presentation

Object-Oriented Software Design (COMP 304) 7 January 2005

Object-Oriented Software Design and Software Processes

Hans Vangheluwe

Modelling, Simulation and Design Lab (MSDL) School of Computer Science, McGill University, Montr´ eal, Canada

Hans Vangheluwe hv@cs.mcgill.ca 1/17

Overview

• 1. Software Processes
• 2. The Process influences Productivity
• 3. The Rational Unified Process (RUP)
• 4. Extreme Programming (XP)

Hans Vangheluwe hv@cs.mcgill.ca 2/17

Software Processes

“The Software Engineering process is the total set of Software Engineering activities needed to transform requirements into software”.

Watts S. Humphrey. Software Engineering Institute, CMU. h t t p : / / p

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Some Software Processes:

• Waterfall model
• Spiral model
• Throwaway/Evolutionary prototyping model
• Incremental/iterative development
• Automated software synthesis
• . . .

Hans Vangheluwe hv@cs.mcgill.ca 3/17

The Waterfall Model (W. Royce. 1970)

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The Process influences Productivity

“Adding manpower to a late software project makes it later”.

Fred Brooks. The Mythical Man-Month. h t t p : / / w w w . e r c b . c

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/ f e a t u r e / f e a t u r e . 0 0 1. h t m l

Hans Vangheluwe hv@cs.mcgill.ca 5/17

Why Brooks’ Law ? Team Size.

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Hans Vangheluwe hv@cs.mcgill.ca 6/17

Why Brooks’ Law ? Programmer Behaviour.

Eystein Fredrik Esbensen’s COMP 522 project. h t t p : / / w w w . s t u d . n t n u . n

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Hans Vangheluwe hv@cs.mcgill.ca 7/17

Why Brooks’ Law ? Productivity.

Hans Vangheluwe hv@cs.mcgill.ca 8/17

Why Brooks’ Law ? Remaining work.

Hans Vangheluwe hv@cs.mcgill.ca 9/17

The Rational Unified Process (RUP): Activity Workload as Function of Time

Hans Vangheluwe hv@cs.mcgill.ca 10/17

The Rational Unified Process (RUP): Observations

• 1. Waterfall-like sequence of

Requirements, Design, Implementation, Testing.

• 2. Not pure waterfall:
• Iteration
• Overlap (concurrency) between activities
• 3. Testing:
• Regression (test not only newly developed, but also previously

developed code)

• Testing starts before design and coding (Extreme Programming)

Hans Vangheluwe hv@cs.mcgill.ca 11/17

The Rational Unified Process (RUP)

Hans Vangheluwe hv@cs.mcgill.ca 12/17

Extreme Programming (XP)

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Hans Vangheluwe hv@cs.mcgill.ca 13/17

Extreme Programming (XP) highlights

• User Stories are written by the customers as things that the system

needs to do for them. They drive the creation of acceptance tests.

• The project is divided into Iterations.

Hans Vangheluwe hv@cs.mcgill.ca 14/17

Extreme Programming (XP) highlights

Use Class, Responsibilities, and Collaboration (CRC) Cards to design the system.

Hans Vangheluwe hv@cs.mcgill.ca 15/17

Extreme Programming (XP) highlights

• Code the Unit Test first.
• All code must have Unit Tests; All code must pass all unit tests

before it can be released.

• Refactor whenever and wherever possible.

Hans Vangheluwe hv@cs.mcgill.ca 16/17

Extreme Programming (XP) highlights

Pair Programming

Hans Vangheluwe hv@cs.mcgill.ca 17/17