1. Ch 1: The Scope of Software Engineering
CSCI 4320

2. What is “Software Engineering”?
A discipline whose aim is the production of software that
meets the client’s needs
fault-free
delivered on time
delivered within budget
easy to modify

3. Why the need for Software Engineering?
Software Crisis: Unacceptable low quality of software, exceeds deadline and budget.
*Completed late, over budget, and/or with features missing
The outcomes of 280,000 development projects completed in 2000

4. Horror Stories
Patients died as a consequence of severe overdoses of radiation.
US Treasury Department mailed incorrectly printed Social Security Checks.
Interest miscalculated on student loans resulting in higher monthly payments.
Mars Climate Orbiter spacecraft crashes into the surface of Mars because of measurement conversion error.
Consequences of software failures range from inconvenience to death!

5. Ideal SE Life Cycle
Theoretical description of the steps that should be performed when building a software product
Requirements
Analysis (specification)
Draw up the Software Project Management Plan
Design
Architectural and Detailed Design
Implementation
Coding, Testing, Integration, Accepted by Clients
Post-delivery maintenance
Corrective, perfective (i.e. faster), adaptive (i.e. new hardware)
Retirement

6. Classical vs. Modern Views of Maintenance
Development-then-Maintenance model
Modern:
Maintenance is performed at any time
Projects take a long time and clients requirements change during process
No longer from scratch - Reuse of existing products is widespread

7. Post-Delivery Maintenance
The real-time world is constantly changing
Bad products are thrown away.
Good products are repaired and enhanced
SE Goal: Reduce post-delivery maintenance cost!
Average cost of percentages of development and post-delivery maintenance between 1992 and 1998.

8. Find Faults Early!
The cost of correcting a fault increase steeply from requirements to post-delivery maintenance
Involves: update documents, edit code, testing, integration …
60-70% of all faults detected are requirements, analysis or design
SE Goal: Better requirements, specifications and designs

9. Importance of Continual Planning, Testing, Documentation
After customer has signed off on the specifications, continue to monitor and adjust plan.
Software must be fault-free as possible at all times.
At all times, documentation must be complete, correct and up-to-date.
personnel overturn
incomplete implementation
inaccurate testing
impossible to maintain

10. Why use Object-Oriented Paradigm
Classical Structured Paradigm
Focus on functions of system
Object-Oriented
Focus on objects
Implementation details are local to the object
Regression fault (inadvertent fault produced by seeming unrelated change) is greatly reduced.
Encapsulation: well-designed independent units
Potential Reuse of objects reduces time and cost

11. Code of Ethics
Ethics – moral standards that help guide your behavior, actions and choices
The golden rule: Do unto others as you would have them do unto you
The slippery-slope rules: Be careful starting down a path because one you start you may not be able to stop
Professional codes of conduct (ACM, IEEE)
Contribute to society and human well being
Avoid harm to others
Be honest and trustworthy
Honor property rights including copyrights and patents
Give proper credit for intellectual property
Access computing resources only when authorized
Respect privacy of others.

12. Questions
When is it better to find faults? (requirements, post-delivery maintenance)
You are in charge of computerizing the extraction process in a silver refinery. The cost of development has been estimated to be $370,000. Approximately how much additional cost will be needed for post-delivery maintenance?