01 - Introduction to Software Engineering 140901

8/11/2019 01 - Introduction to Software Engineering 140901

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Faculty of Computer ScienceUniversity of Indonesia

Topic 01:Introduction toSoftware Engineering


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Outline

What is Software?

What is Software Engineering? The Essence of Software EngineeringPractice


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Characteristics of Software

1. Software is developed or engineered , it isnot manufactured in the classical sense.

2. Software doesn't "wear out" - itsdeteriorate .

Hardware failure rate depicted in a form ofthe bathtub curve

Software failure rate depicted in a form ofthe idealized curve.

3. Although the industry is moving toward

component-based construction, mostsoftware continues to be custom-built.


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Failure Curve for Hardware: Bathtub Curve

(Source: Pressman)

Time

Infant mortality Wear out

F a

i l u r e r a

t e


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Failure Curve for Software

(Source: Pressman)


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Software Application

System software Application software Engineering/scientific software Embedded software Product-line software WebApps (Web applications)

AI software


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What is Software Engineering?

Software engineers often encounterproblems related to a computer or existingcomputer system but sometimes theunderlying problem have nothing to do withcomputers

Therefore, we must understand the natureof the problem first:Do not impose computing machinery ortechniques on every problems.

Solve the problem first and if needed we can

use technology as a tool to implement oursolution.


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Solving problems:Begin investigating a problem by analyzing it.

Break the problem in pieces that we understandand try to deal with.

Understand the relationship between pieces thathold the problem.

Once analyzed, construct the solution from thecomponents that address the problems variousaspects.

This reverse process is called synthesis :

putting together of a large structure from smallbuilding blocks.


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Analyzing Problem(Source: Pfleeger & Atlee)

PROBLEM

Subproblem 1Subproblem 4

Subproblem 3Subproblem 2

FIGURE 1.1 The process of analysis


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Synthesizing Solution(Source: Pfleeger & Atlee)

SOLUTION

Solution 1Solution 4

Solution 3Solution 2

FIGURE 1.2 The process of synthesis


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In solving a problem, we employ a varietyof methods , tools , procedures andparadigms .

Method or technique: a formal procedure forproducing some results.

Tool: an instrument or automated system foraccomplishing something in a better way.

Procedure: a combination of tools andtechniques that, in concert, produce aparticular product.

Paradigm: a particular approach orphilosophy for building software.


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Seminal definition:[Software engineering is] the establishment and

use of sound engineering principles in orderto obtain economically software that is reliableand works efficiently on real machines.

IEEE definition:Software Engineering:

(1) The application of a systematic, disciplined,quantifiable approach to the development,operation, and maintenance of software; that is,the application of engineering to software.

(2) The study of approaches as in (1).


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Relationship Between Software Engineering andComputer Science

Source: Pfleeger & Atlee

COMPUTERSCIENCE CUSTOMER

SOFTWAREENGINEERING

Theories Computer Functions

Problem

Tools andTechniques toSolve Problem

FIGURE 1.3 The relationship betweencomputer science and software engineering


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A Layered Technology

Software Engineering


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Process

Process layer is the foundation .the glue that holds the technology layerstogether

enables rational and timely development

defines frameworkforms the basis for management control ofsoftware project

establishes the context in which technicalmethods are applied, work products areproduced, milestone are established, qualityis ensured, and change is properly managed.


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Method

Method layer provide the technical how-tos forbuilding software

encompass a broad array of tasks

(include communication, requirementanalysis, design modeling, programconstruction, testing, and support)

rely on a set of basic principles thatgovern each area of the technology andinclude modeling activities and otherdescriptive techniques.


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Tools

Tools layer provide automated or semiautomatedsupport for the process and the methods


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Framework Activities

Communication Planning Modeling

Requirement analysis & definitionDesign

Architecture design / System design

Component design / Program design

ConstructionCode generation

Testing

Unit testing

Integration testing

System testing

DeploymentSystem deliveryMaintenance


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The Essence of Practice

Polya suggests:1. Understand the problem ( communication

and analysis ).

2. Plan a solution ( modeling and softwaredesign ).

3. Carry out the plan ( code generation ).4. Examine the result for accuracy ( testing

and quality assurance ).


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Understand the Problem

Who has a stake in the solution to theproblem? That is, who are the stakeholders?

What are the unknowns? What data,functions, and features are required to properlysolve the problem?

Can the problem be compartmentalized? Isit possible to represent smaller problems that

may be easier to understand? Can the problem be representedgraphically? Can an analysis model be

created?


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Plan the Solution

Have you seen similar problems before? Arethere patterns that are recognizable in apotential solution? Is there existing software thatimplements the data, functions, and featuresthat are required?

Has a similar problem been solved? If so, areelements of the solution reusable? Can subproblems be defined? If so, are

solutions readily apparent for the subproblems? Can you represent a solution in a manner

that leads to effective implementation? Cana design model be created?


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Carry Out the Plan

Does the solution conform to theplan? Is source code traceable to thedesign model?

Is each component part of thesolution provably correct? Has thedesign and code been reviewed, orbetter, have correctness proofs beenapplied to algorithm?


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Examine the Result

Is it possible to test each componentpart of the solution? Has a reasonabletesting strategy been implemented?

Does the solution produce resultsthat conform to the data, functions,and features that are required? Hasthe software been validated against allstakeholder requirements?


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Q & A

Documents

01 - Introduction to Software Engineering 140901