ch1 ian sommerville

8/4/2019 Ch1 Ian Sommerville

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Ian Sommerville 2004 Software Engineering, 7th edition. Chapter 1 Slide 1

An Introduction to SoftwareEngineering

(CS 4320)


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Instructor

Ye Duan (321 Engr West)

Interests: Computational Graphics and

Biomedical Imaging

Email: [email protected] Office Hours: Monday 3-5pm
mailto:[email protected]:[email protected]


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Malik Al Jarad Tubaishat

Office hours: Monday 2-3pm; Thursday 10-11am

Email: [email protected]

Room: 242 EBWYongjian Xi

Office hours: Monday 1-2pm; Friday 1-2pm

Email: yxry2@mizzou

Room: 242 EBW

Teaching Assistants
mailto:[email protected]:[email protected]:[email protected]


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Class Hours: TR 11:00 AM -12:15 PM

Room: Lafferre Hall (EBE) E1419.

(245 EBW on April 12)

Textbook: Software Engineering, by Sommerville,Ian, 7th Edition, Addison Wesley, 2004.

Prerequisites: CS 2050 - Algorithm Design andProgramming II

Home Pages:http://www.cs.missouri.edu/~duan/cs4320.html

Other course info
http://www.cs.missouri.edu/~duan/cs4320.htmlhttp://www.cs.missouri.edu/~duan/cs4320.html


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Assignments and Exams

Homework: 3 homework assignments throughoutthe semester. These assignments will usually betaken from the exercises at the end of eachchapter in the course textbook.

Exams: There will be two closed-book exams.Class notes will not be allowed during the exams.The format of the exams will be mixed with some

multiple choice, true/false, short answer, anddiagram-based questions.



Final project - 1

Primary focus of this class (problem-basedlearning)

Students are expected to work together in groups

of 3-4 members and produce a working system

for a real-world client.

The client may be a business, organizations,instructor, friend or relative, so long as they can

provide a list of requirements.



Students are expected to document their entiresoftware process, demonstrate their finishedproduct, and provide a plan for systemmaintenance and support.

Please see the instructor or teaching assistantsearly in the semester if you are having difficultyfinding a client or other group members.

3 phases

Phase I due on 9/15

Final project - 2



Phase I report

Team member list

Contact person (for communication withinstructor and TAs)

Project plan (meeting every week) Project description (after talking to users)

Overview

Objectives

Scope

Benefits,



Grading

Homework assignments 20% (6%, 7%, 7%)

Exam 1 20%

Exam 2 20%

Final Project 40% 10% from peers (students)

15% presentation

15% report

Reduction in score by poor evaluation from other teammembers in the same team.


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How to get maximum from your tuition

Attend class regularly

Read the related chapters in the textbook

Do your homework assignment independently

(dont use google) Visit teaching staff whenever you have questions

Work on the final project every week

Think more!

-- schedule


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Objectives

To introduce software engineering and to explainits importance

To set out the answers to key questions aboutsoftware engineering

To introduce ethical and professional issues and

to explain why they are of concern to softwareengineers


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Topics covered

FAQs about software engineering

Professional and ethical responsibility


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Software engineering

The economies of ALL developed nations aredependent on software.

More and more systems are software controlled

Software engineering is concerned with theories,

methods and tools for professional softwaredevelopment.

Expenditure on software represents asignificant fraction of GNP in all developed

countries.


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Software costs

Software costs often dominate computer systemcosts. The costs of software on a PC are oftengreater than the hardware cost.

Software costs more to maintain than it does to

develop. For systems with a long life,maintenance costs may be several timesdevelopment costs.

Software engineering is concerned with cost-effective software development.


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What is software?

What is software engineering?

What is the difference between software

engineering and computer science? What is the difference between software

engineering and system engineering?

What is a software process?

What is a software process model?


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What are the costs of software engineering?

What are software engineering methods?

What is CASE (Computer-Aided Software

Engineering) What are the attributes of good software?

What are the key challenges facing software

engineering?


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What is software?

Computer programs and associated documentation suchas requirements, design models and user manuals.

Software products may be developed for a particularcustomer or may be developed for a general market.

Software products may be Generic - developed to be sold to a range of different customers

e.g. PC software such as Excel or Word.

Custom - developed for a single customer according to theirspecification.

New software can be created by developing new

programs, configuring generic software systems orreusing existing software.


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What is software engineering?

Software engineering is an engineering disciplinethat is concerned with all aspects of softwareproduction.

Software engineers should adopt a systematic

and organised approach to their work and useappropriate tools and techniques depending onthe problem to be solved, the development

constraints and the resources available.


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What is the difference between softwareengineering and computer science?

Computer science is concerned with theory andfundamentals; software engineering is concernedwith the practicalities of developing anddelivering useful software.

Computer science theories are still insufficient toact as a complete underpinning for softwareengineering (unlike e.g. physics and electrical

engineering).

Wh i h diff b f


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What is the difference between softwareengineering and system engineering?

System engineering is concerned with allaspects of computer-based systemsdevelopment including hardware, software andprocess engineering. Software engineering is

part of this process concerned with developingthe software infrastructure, control, applicationsand databases in the system.

System engineers are involved in systemspecification, architectural design, integrationand deployment.


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What is a software process?

A set of activities whose goal is the developmentor evolution of software.

Generic activities in all software processes are: Specification - what the system should do and its

development constraints Development - production of the software system

Validation - checking that the software is what thecustomer wants

Evolution - changing the software in response to

changing demands.


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What is a software process model?

A simplified representation of a software process,presented from a specific perspective.

Examples of process perspectives are

Workflow perspective - sequence of activities;

Data-flow perspective - information flow; Role/action perspective - who does what.

Generic process models

Waterfall;

Iterative development;

Component-based software engineering.


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What are the costs of software engineering?

Roughly 60% of costs are development costs,40% are testing costs. For custom software,evolution costs often exceed development costs.

Costs vary depending on the type of system

being developed and the requirements of systemattributes such as performance and systemreliability.

Distribution of costs depends on the

development model that is used.


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Activity cost distributionWat erfall model

Iterative development

Component-based software eng ineering

Development and evolution costs for long-lifetime syst ems

Syst em evolu tion

10 200 30 4000

Syst em develop ment

Sp eci fi cat io n Desi gn Develo pment Int eg rat ion and t es tin g

25 50 75 1000

Specification Development Integ ration and testing

2 5 50 75 1000

Specification Iterative d evelopmen t System testing

2 5 50 75 1000


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Product development costs

Specification Developmen t System testing

25 50 75 1000


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What are software engineering methods?

Structured approaches to software development whichinclude system models, notations, rules, design adviceand process guidance.

Model descriptions Descriptions of graphical models which should be produced;

Rules Constraints applied to system models;

Recommendations Advice on good design practice;

Process guidance What activities to follow.

What is CASE (Computer Aided Software


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What is CASE (Computer-Aided SoftwareEngineering)

Software systems that are intended to provide automatedsupport for software process activities.

CASE systems are often used for method support.

Upper-CASE

Tools to support the early process activities of requirementsand design;

Lower-CASE

Tools to support later activities such as programming,debugging and testing.


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What are the attributes of good software?

The software should deliver the required functionality andperformance to the user and should be maintainable,dependable and acceptable.

Maintainability Software must evolve to meet changing needs;

Dependability Software must be trustworthy;

Efficiency Software should not make wasteful use of system resources;

Acceptability Software must accepted by the users for which it was designed.

This means it must be understandable, usable and compatiblewith other systems.

What are the key challenges facing software


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What are the key challenges facing softwareengineering?

Heterogeneity, delivery and trust.

Heterogeneity

Developing techniques for building software that can cope withheterogeneous platforms and execution environments;

Delivery Developing techniques that lead to faster delivery of software;

Trust

Developing techniques that demonstrate that software can betrusted by its users.


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Professional and ethical responsibility

Software engineering involves widerresponsibilities than simply the application oftechnical skills.

Software engineers must behave in an honest

and ethically responsible way if they are to berespected as professionals.

Ethical behaviour is more than simply upholdingthe law.


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Issues of professional responsibility

Confidentiality Engineers should normally respect the confidentiality

of their employers or clients irrespective of whetheror not a formal confidentiality agreement has beensigned.

Competence Engineers should not misrepresent their level of

competence. They should not knowingly accept workwhich is outwith their competence.


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Issues of professional responsibility

Intellectual property rights Engineers should be aware of local laws governing the use of

intellectual property such as patents, copyright, etc. Theyshould be careful to ensure that the intellectual property ofemployers and clients is protected.

Computer misuse Software engineers should not use their technical skills to

misuse other peoples computers. Computer misuse ranges

from relatively trivial (game playing on an employers machine,

say) to extremely serious (dissemination of viruses).


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ACM/IEEE Code of Ethics

The professional societies in the US havecooperated to produce a code of ethical practice.

Members of these organisations sign up to thecode of practice when they join.

The Code contains eight Principles related to thebehaviour of and decisions made by professionalsoftware engineers, including practitioners,educators, managers, supervisors and policymakers, as well as trainees and students of theprofession.


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Code of ethics - preamble

Preamble The short version of the code summarizes aspirations at a high

level of the abstraction; the clauses that are included in the fullversion give examples and details of how these aspirationschange the way we act as software engineering professionals.Without the aspirations, the details can become legalistic and

tedious; without the details, the aspirations can become highsounding but empty; together, the aspirations and the detailsform a cohesive code.

Software engineers shall commit themselves to making theanalysis, specification, design, development, testing andmaintenance of software a beneficial and respected profession.

In accordance with their commitment to the health, safety andwelfare of the public, software engineers shall adhere to thefollowing Eight Principles:


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Code of ethics - principles

PUBLIC Software engineers shall act consistently with the public

interest.

CLIENT AND EMPLOYER

Software engineers shall act in a manner that is in the best

interests of their client and employer consistent with the publicinterest.

PRODUCT

Software engineers shall ensure that their products and relatedmodifications meet the highest professional standards possible.


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JUDGMENT Software engineers shall maintain integrity and independence

in their professional judgment.

MANAGEMENT

Software engineering managers and leaders shall subscribe to

and promote an ethical approach to the management ofsoftware development and maintenance.

PROFESSION

Software engineers shall advance the integrity and reputation ofthe profession consistent with the public interest.


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COLLEAGUES Software engineers shall be fair to and supportive of

their colleagues.

SELF

Software engineers shall participate in lifelonglearning regarding the practice of their professionand shall promote an ethical approach to the practiceof the profession.


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Ethical dilemmas

Disagreement in principle with the policies ofsenior management.

Your employer acts in an unethical way andreleases a safety-critical system without finishing

the testing of the system.

Participation in the development of militaryweapons systems or nuclear systems.


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Key points

Software engineering is an engineering discipline that isconcerned with all aspects of software production.

Software products consist of developed programs andassociated documentation. Essential product attributesare maintainability, dependability, efficiency and usability.

The software process consists of activities that areinvolved in developing software products. Basic activitiesare software specification, development, validation andevolution.

Methods are organised ways of producing software. They

include suggestions for the process to be followed, thenotations to be used, rules governing the systemdescriptions which are produced and design guidelines.


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Key points

CASE tools are software systems which are designed tosupport routine activities in the software process such asediting design diagrams, checking diagram consistencyand keeping track of program tests which have been run.

Software engineers have responsibilities to theengineering profession and society. They should notsimply be concerned with technical issues.

Professional societies publish codes of conduct which setout the standards of behaviour expected of their

members.

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