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Introduction

Complex and large SW. SW crises.

1950 1960 1970 1980 1990 2000

Expensive HW.

Custom SW.

Batch execution

Structured programming

Product SW.

Data orientation

Expert systems

AIdistributed systems

parallel programming

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Introduction

Software Engineering is concerned with

theories, methods and tools needed todevelop high quality software products in a

cost effective way.

Cost effective:

limited resources.

Time schedule.

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System Development Life Cycle

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System Development Life Cycle

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Software Development Life Cycle

Maintenance is an ongoing process over

the system life

60% of the time is spent on maintenance

and 40% on the development Correct errors

Add new features (business changes)

Adapt to environment changes

Cost of correcting errors increase as you

move in the life cycle

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Amount of resources consumed over the life cycle

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CategoriesInformation systems fall into one of the following

eight categories: Transaction processing systems (TPS).

Office automation systems (OAS).

Knowledge work systems (KWS).

Management information systems (MIS). Decision support systems (DSS).

Expert systems (ES) and Artificial Intelligence (AI).

Group decision support systems (GDSS) and Computer-

Supported Collaborative Work Systems. Executive support systems (EES).

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System Analysis and Design

A systematic approach of: Identifying problems and opportunities

Analyzing the flow of information in organization

Design computerized system to solve the

problem

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System Analyst

A problem solver that requires

communication skills, management skillsand technical skills

An agent of change Either:

An outside consultant

A supporting expert within the organization

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System Analysis and Design

Methodologies

Systematic approaches of performing

analysis and design

Structured:

Based on showing the flow of data in theorganization

Object-Oriented:

Describes the objects interacting in theorganization

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Organizations as Systems

Interrelated subsystems

Product based

Service based

Organization

Goals

input Output

System environment

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Organizations

Organizations are composed of

interrelated and interdependentsubsystems.

System and subsystem boundaries andenvironments impact on information

system analysis and design.

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Organizations as Systems Organization Environment:

Physical Economical

Political (rules and regulations)

Feedback from environment and inside theorganization to control and plan performance

Organization Structure and Culture: Culture: how people interrelate

Open organization: flow of information within organization

Management levels

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Open and Closed Systems

Systems are described as either

Open

Free-flowing information.

Output from one system becomes input to another.

Closed with restricted access to information

Limited by numerous rules.

Information on a need to know basis.

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Managerial Control

The three levels of managerial control are:

Operations management.

Middle management.

Strategic management.

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Project Initiation

Projects are initiated for two broad

reasons: Problems that lend themselves to systems

solutions.

Opportunities for improvement through

Upgrading systems.

Altering systems.

Installing new systems.

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Identifying Problems

Look for situations where the goals of the

organization has not been met

Check the output against performance

criteria (e.g. errors and slow output)

Observe behavior of employee (e.g.absence, turnover)

Listen to external feedback fromcustomers and vendors

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Opportunities for improvement Speed up a process

Duplicated steps

Combining processes

Reducing errors in input Reducing redundant output

Improving integration of systems

Improving workers satisfaction

Improving customer or vendor interactions with the

system

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Feasibility Study

Done by the system analyst

Done quickly with minimum resources

Interview high management people

Define the objectives of the project &organization

Output is feasibility report

The decision whither to take the project is

management

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Feasibility Study

Helps the organization attain overall

objectives

Is possible to accomplish with present

organizational resources in the following

three areas:

Technical Feasibility:

Economic Feasibility Operational Feasibility

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Technical Feasibility

Technical feasibility assesses whether the

current technical resources are sufficientfor the new system.

If they are not available, can they be

upgraded to provide the level of

technology necessary for the new system.

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Economic Feasibility

Economic feasibility determines whether

the time and money are available todevelop the system.

Includes the purchase of:

New equipment.

Hardware.

Software.

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Operational Feasibility

Operational feasibility determines if the

human resources are available to operatethe system once it has been installed.

Users that do not want a new system may

prevent it from becoming operationally

feasible.

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Feasibility Impact Grid (FIG) A feasibility impact grid (FIG) is used to

assess the impact of any improvements tothe existing system.

Current or proposed systems are listed on the

left.

Objectives are listed on the top.

Red arrows indicate a positive impact.

Green arrows indicate implementation.

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Computer-aided software

Engineering tools

Software packages that support the software

development process Advantages:

Improves quality and productivity

Facilitate communication among team membersand users

Provides continuity between life cycle phases

Facilitate maintenance

But, they should be carefully chosen andstaff should be properly trained.

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Computer-aided software

Engineering tools

May be divided into several categories:

Upper CASE: perform analysis and design

Lower CASE: generate computer source code

Integrated CASE

Other ways of classification

Functional

Breadth

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Project Management Activities:

Selection of team members

Assignment of tasks to people

Estimate task time

Schedule project plan

Writing system proposal

Control by monitoring plan against activities Motivating Team members

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Project Planning Project is broken down into phases.

Further project is broken down into tasks oractivities.

Finally project is broken down into steps or even

smaller units. Time is estimated for each task or activity.

Most likely, pessimistic, and optimistic estimates

for time may be used.

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Scheduling tools Gantt chart: Shows activities over a period of

time as bars on a graph PERT-Program Evaluation and Review

Technique PERT diagrams show precedence, activities that

must be completed before the next activities may bestarted.

Once a diagram is drawn it is possible to identify thecritical path, the longest path through the activities.

Monitoring critical path will identify shortest time tocomplete the project.

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Gantt Chart Example

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PERT Diagram Example