Lawrence Chung Software Engineering: Introduction 1 Module 1: Introduction to Software Engineering

Lawrence Chung Software Engineering: Introduction 1

Module 1: Introduction to Software Engineering


Objectives

What is Software Engineering?

Why Software Engineering?

How to do Software Engineering?



Software Engineering = Software + Engineering

What is Software?

Software = Soft + ware

Any examples?

What is Engineering?

Engineering = Engine-er-ing

Any examples?

Is this an Engineering discipline? If yes, why? If not, why not?

Is this for an Engineer or a scientist?



A historical definition:

“The establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines …” [Fritz Bauer, at the 1st NATO Conference on Software Engineering, 1969]

IEEE definition:

“Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.”

A shorter definition: BCFH



Used w. extensive rework, but later abandoned20%

Used as delivered 2%

Usable w. rework3%

9 software projects totaling $96.7 million: Where The Money Went [Report to Congress, Comptroller General, 1979]

Delivered, but never successfully used45%

Paid for, but not delivered30% Why?

Software hurtsRequirementsdesign


What Factors Contribute to Project Success?

10. Other

9. Reliable Estimates

8. Formal Methodology

7. Firm Basic Requirements

6. Standard Software Infrastructure

5. Minimized Scope

4. Clear Business Objectives

3. Experienced Project Manager

2. User Involvement

1. Executive Management Support

The CHAOS CHAOS Ten

Standish Group, ‘01 (www.standishgroup.com)

Project Success Factors

28%

49%

23%

completed on time and on budget

canceled before completion

overran original estimates:-Time overrun averaged 63%- Cost overrun averaged 45%


What Factors Contribute to Project Failure?

Standish Group, ‘01 (www.standishgroup.com)

The CHAOS CHAOS TenThe CHAOS CHAOS Ten

“The definition of insanity is doing the same thing over and over again and expecting a different result.” [Albert Einstein]



Work alone20%

What do software engineers do?

Non-productiveActivities30%

Interaction50%

programming ≠ software engineeringpersonal activity team activity

small, clear problem large, nebulous problem



http://www.cis.gsu.edu/~mmoore/CIS3300/handouts/SciAmSept1994.html

http://techdirt.com/articles/20060818/1613226.shtml

Are you aware of any other mishaps?



Major symptoms of the “software crises”:

Over budget Schedule slippage Poor quality

Major causes of the “software crises”:

The "software crises" came about when people realized the major problems in software development were … caused by communication difficulties and the management of complexity” [Budd]


Why SE?


Systems Engineering

Requirements Analysis

Project Planning

Architectural Design

Detailed Design

Implementation

Release

Maintenance

Quality A

ssurance

Software Lifecycle Review

How to Do Software Engineering?

BCFH - models/languages,

processes/methodologies, tools, …


To be discussed later on…


How to do SE?


How to do SE?


The Tar Pit

The woes of the craft:Bugs!!!Bugs get harder as testing progressesThe fundamental problem: fixing a bug has a

20%-50% chance of introducing anotherThe product gets obsolete upon or even before

completionWorse: must use others’ programs!

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Genesis 11:1-9 Acts 2:1-4The Tower Of Babel

Let's become famous by building a city with a tower that reaches up to heaven (verse four).

Let's go down and confuse their speech right away, and make it so that they will not understand each other's speech. (verses five through seven).


Why Did the Tower of Babel Fail?

Bad communication in software projects

is the root of all evil.


The Mythical Man-Month

Optimism:All programmers are optimists, believing in

happy endings and fairy god-mothers.Because programming tasks are usually

chained end-to-end, the probability that each will go well is very small.

Man-month:Cost vary as a product: men ·

months.

Progress does not: communication overhead!Overhead: intercommunication and training.

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Brook’s Law

Adding manpower to a late software project makes it later.


Hatching a Catastrophe

Poor Project planning, estimation, controlCoding is “90% finished” for half of the total

coding timeDebugging is “99% complete” most of the

time


No Silver Bullet – Essence and Accident in Software Engineering

“There is no single development, in either technology or management technique, which by itself promises even one order-of-magnitude improvement within a decade in productivity, in reliability, in simplicity” (1986).

Complexity enormous number of states (orders of magnitude more than in

hardware), so conceiving, describing and testing is hard increases non-linearly with its size introduces a lot of difficulties:

communication among team members enumerating (much less understanding) of all possible states of the

program management problems:

conceptual integrity is hard to achieve learning curve: personnel turnover becomes disaster

others


The M-MM after 20 years

Answers questions like: What do you now think was wrong when written? What is now obsolete? What is really new in the software engineering world?

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What was right and still is: Conceptual integrity is the more important

factor in ease of use [There are other factors. Consider Macintosh vs. MS-DOS].It is the central question addresses by M-MM and is central to product quality.


How to do SE?


How to do SE?


How to do SE?


How to do SE?


How to do SE?


How to do SE?


Why speak about management

rather than technical issues?


How to do SE?

News Groups:

comp.software-engcomp.software.testing…

Professional Organizations:IEEE: TSE, ICSE, ICRE, …ACM: TOSEM…


Introduction to SE - Summary

Why Software Crisis due to Communication and Complexity Inherent complexity

What Engineering (large) software, bcfh

How BCFH languages, concepts, models, tools









Introduction to SE - Points to Ponder

1. Programming = software engineering?2. What does BCFH really mean? Can you define it

completely?3. What are the similarities, and differences, between

Civil Engineering and Software Engineering? 4. What are the differences between a notation and a

methodology?5. Can we use C# for analysis?6. Can you prove you and I communicate with each

other perfectly?7. Are you a scientist or an engineer?

Documents

Lawrence Chung Software Engineering: Introduction 1 Module 1: Introduction to Software Engineering