INTRODUCTION TO SOFTWARE ENGINEERING

ALNEELAIN UNIVERSITY SOFTWARE ENGINEERING

DEPT.

Prepared By: Ahmed Alageed

1

1- INTRODUCTION

COURSE DETAILS

This Course will cover the following Topics: Introduction. Software Process Models. Requirements Analysis & Specification Design Coding

2

COURSE DETAILS

Testing Maintenance Computer Aided Software Engineering

(CASE) Software quality assurance Managing Software Projects

3

LEARNING OBJECTIVES

After successfully completing the module student should be : explain the software engineering

principles and techniques that are used in developing quality software products

apply software engineering principles and techniques appropriately to develop moderately complex software system

4

ASSESSMENT METHOD

The assessment method will be as following: Final Exam: 60% Med-Term Exam:20% Tutorial & Presentation:20% ( including

The Lab. Remarks & attendance.

5

COURSE LAB.

In the practical part of this course you will learn how to use CASE tools (UML) in addition to do some tutorial related to the course subjects.

6

CONTACT INFO. You can contact me at any time by

Email:Aalageed@neelain.edu.sd

I will be available at my office on Sat. from 12:00 PM to 2:00 PM

7

COURSE REFERENCES

Main Reading:1. Software Engineering by Ian

Sommerville, 8th edition, Addison-Wesley, 2006.

2. Software Engineering: A practitioner's approach by Roger S. Pressman, 6th edition, McGraw-Hill International edition, 2005.

8

COURSE REFERENCES Supplementary Reading1. http://portal.acm.org/citation.cfm?

id=1159393

2. http://www.vnunet.com/vnunet/news/2117315/air-traffic-system-already-obsolete

9

1. INTRODUCTION

Instructional Objectives Describe what software is, different types

of software and software quality attributes Describe with the problems associated

with software and software development Define what software engineering is and

explain why it is important State some professional issues related to

software development

10

1.1 SOFTWARE

1.1.1. What is software? [Ref.1: pg. 5-6]

Computer programs and associated documentation such as requirements, design models and user manuals in addition to data structure.

Software products may be developed for a particular customer or may be developed for a general market.

11

1.1.1 WHAT IS SOFTWARE

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 their specification.

New software can be created by developing new programs, configuring generic software systems or reusing existing software.

12

1.1 SOFTWARE

1.1.2. Types of software [Ref.2: pg. 40-41]

System software Application Software. Engineering and scientific software Embedded software Product-line software. Web-based software Artificial intelligence software

13

1.1 SOFTWARE

1.1.3. Characteristics of Software [Ref.2: pg. 36-39] [Ref.4]

Software is differ form any other thing that human beings build.

Software is a logical rather than a physical system element. Therefore software has characteristics that are considerably different than those of hardware.

14

1.1.3. CHARACTERISTICS OF SOFTWARE

Software is developed or engineered; it is not manufactured in the classical sense.

Software doesn’t “wear out”

15

1.1.3. CHARACTERISTICS OF SOFTWARE

16

1.1.3. CHARACTERISTICS OF SOFTWARE Although the industry is moving toward

component-based construction, most software continues to be custom built

17

1.1 SOFTWARE

1.1.4. Attributes of good software [Ref.1: pg. 34-35]

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

Maintainability Software must evolve to meet

changing needs;18

1.1.4. ATTRIBUTES OF GOOD SOFTWARE

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 compatible with other systems.

19

SUCCESSFUL SOFTWARE SYSTEM

Software development projects have not always been successful.

When do we consider a software application successful? Development completed. It’s useful. It’s usable. And it’s used.

20

REASONS FOR FAILURE

Schedule slippage. Cost-over run. Does not solve user’s problem.

21

REASONS FOR FAILURE

Ad hoc software development results in such problems: No planning of development works(e.g no

milestones defined). Deliverables to user not identified. Poor understanding of user requirements. No control or review. Technical incompetence of developers. Poor understanding of cost and effort by

both developer & user.

22

ENGINEERING: OTHER DISCIPLINES Large projects common and

successfully done: Buildings bridges, Dams. Power plants AircraftsEngineering a solution: To design, develop( build, fabricates) an

artifact that meets specifications efficiently, cost- effectively and ensuring quality

Using scientific principles23

ENGINEERING

Requires well-defined approach: repeatable, predictable

24

1.2. SOFTWARE ENGINEERING

1.2.1. What is software engineering? [Ref.1: pg. 29]

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

Software engineers should adopt a systematic and organised approach to their work and use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available.

25

WHAT IS THE DIFFERENCE BETWEEN SOFTWARE ENGINEERING AND COMPUTER SCIENCE?

Computer science is concerned with theory and fundamentals; software engineering is concerned with the practicalities of developing and delivering useful software.

Computer science theories are still insufficient to act as a complete underpinning for software engineering (unlike e.g. physics and electrical engineering).

26

WHAT IS THE DIFFERENCE BETWEEN SOFTWARE ENGINEERING AND SYSTEM ENGINEERING?

System engineering is concerned with all aspects of computer-based systems development including hardware, software and process engineering. Software engineering is part of this process concerned with developing the software infrastructure, control, applications and databases in the system.

System engineers are involved in system specification, architectural design, integration and deployment.

27

WHAT IS A SOFTWARE PROCESS? A set of activities whose goal is the

development or 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 the customer wants Evolution - changing the software in

response to changing demands.28

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.

29

WHAT IS A SOFTWARE PROCESS MODEL? Generic process models

Waterfall; Iterative development; Component-based software engineering.

30

1.2. SOFTWARE ENGINEERING

1.2.2. Software engineering costs [Ref.1: pg. 31-33]

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 system attributes such as performance and system reliability.

31

1.2.2. SOFTWARE ENGINEERING COSTS

Distribution of costs depends on the development model that is used.

32

ACTIVITY COST DISTRIBUTION

33

Waterfall model

Iterative development

Component-based software engineering

Development and evolution costs for long-lifetime systems

System evolution

10 200 30 4000

System development

Specification Design Development Integration and testing

25 50 75 1000

Specification Development Integration and testing

25 50 75 1000

Specification Iterative development System testing

25 50 75 1000

PRODUCT DEVELOPMENT COSTS

34

Specification Development System testing

25 50 75 1000

1.2. SOFTWARE ENGINEERING

1.2.3. What are the key challenges facing software engineering? [Ref.1: pg. 35-36]

Heterogeneity, delivery and trust. Heterogeneity

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

35

1.2.3. WHAT ARE THE KEY CHALLENGES FACING SOFTWARE ENGINEERING?

Delivery Developing techniques that lead to faster

delivery of software; Trust

Developing techniques that demonstrate that software can be trusted by its users.

36

1.2. SOFTWARE ENGINEERING

1.2.5. Professional Practice [Ref.1: pg. 36-39; Ref.2: pg. 128-149]

Confidentiality Engineers should normally respect the

confidentiality of their employers or clients irrespective of whether or not a formal confidentiality agreement has been signed.

Competence Engineers should not misrepresent their

level of competence. They should not knowingly accept work which is outwith their competence.

37

1.2.5. PROFESSIONAL PRACTICE

Intellectual property rights Engineers should be aware of local laws

governing the use of intellectual property such as patents, copyright, etc. They should be careful to ensure that the intellectual property of employers and clients is protected.

38

1.2.5. PROFESSIONAL PRACTICE

Computer misuse Software engineers should not use their

technical skills to misuse other people’s computers. Computer misuse ranges from relatively trivial (game playing on an employer’s machine, say) to extremely serious (dissemination of viruses).

39