Designed and Presented by

Dr. Ayman Elshenawy Elsefy

Dept. of Systems & Computer Eng..

Al-Azhar University

Website: eaymanelshenawy.wordpress.com

Email : eaymanelshenawy@yahoo.com

System Analysis and Design

Ian Sommerville,

Software Engineering, 9th Edition

Pearson Education, Addison-Wesley

Modern Systems Analysis and Design, Third Edition Jeffrey A. Hoffer, Joey F. George, Joseph S. Valacich

System

1.3

an interrelated set of business procedures used within one business unit working together for a purpose.

System: Turns data into information and includes:

Hardware and system software

Documentation and training materials

Job roles associated with the system

Controls to prevent theft, The people who use the software

Characteristics of a System

A system has nine characteristics

Components, Interrelated Components

Boundary

Purpose

Environment

Interfaces

Constraints

Input

Output

1.4

1.5

Decomposition

The process of breaking down a system into smaller components

Allows the systems analyst to:

Break a system into small, manageable and understandable subsystems

Focus on one area at a time, without interference from other areas

Concentrate on one group of users without confusing users with unnecessary details

Build different components at independent .

1.6

Important System Concepts

Important System Concepts Modularity

Process of dividing a system into modules of a relatively uniform size

Coupling

Subsystems that are dependent upon each other are coupled

Systems Integration

Developers assemble systems by choosing and implementing specific modules.

an enterprise-wide system may handle all human resources management, payroll, benefits, and retirement functions within a single, integrated system.

organizations develop systems in-house anymore.

1.8

Information Systems Analysis and Design

A method used by companies to create and maintain

SW systems that perform basic business functions

(example, to improve employee efficiency by applying

software solutions to key business tasks)

The result is the application Software that is designed to support specific organizational functions or processes

1.7

Software engineering

Software engineering is concerned with theories,

methods and tools for professional software

development.

Concerned with all aspects of software production

from the early stages of system specification through

to maintaining the system after it has gone into use

10

Importance of Software engineering

Persons and society rely on advanced SW systems.

It is usually cheaper, in the long run, to use software

engineering for software systems rather than just write

the programs as if it was a personal programming

project.

Software Engineering Process

Used to create an information system, Consists of:

Methodologies: A sequence of step-by-step approaches that help develop the SW system

Techniques: Processes that the analyst follows to ensure thorough, complete and comprehensive analysis and design

Tools: Computer programs that aid in applying techniques

1.11

Three key components of an information system Data , Data Flows , Processing Logic

1.12

Data (raw facts)

Understand the source and use of data is key to good

system design

Various techniques are used to describe data and the

relationship amongst data

Data Flows

Groups of data that move and flow through the system

Include description of sources and destination for each data

flow

Processing Logic

steps that transform data and events that trigger the steps

Databases and Application Independence

Database

Shared collection of logically related data

Organized for storage and retrieval by multiple users

Centrally managed

Designed around subjects ( Customers, Suppliers)

Application Independence

Separation of data and definition of data from applications

1.13

Organizational Responsibilities in

Systems Development

1.14

Systems Analysts work in teams includes:

• IS Manager • Programmers • Users • Other specialist

Characteristics of Successful Teams

• Diversity of backgrounds • Tolerance of diversity • Clear and complete communication • Trust • Mutual Respect • Reward structure that promotes shared

responsibility

IS Manager

Involved in allocating resources to and overseeing system development projects.

Programmers

Convert specifications into instructions that the computer understands

Write documentation and testing programs

Business Managers

Have power to fund projects and allocate resources

Set general requirements and constraints for projects.

1.16

Systems Analyst Key individuals in the systems development process

performs analysis and design based upon:

• Understand organization’s objectives, structure and processes

• Know how to exploit information technology for advantage

Skills of a Successful Systems Analyst Analytical: Understanding of organizations, Problem solving

skills and System thinking

Technical : Understanding of potential and limitations of technology

Management: Ability to manage projects, resources, risk and change

Interpersonal : Effective written and oral communication

Copyright 2006 Prentice-

Hall, Inc.

Your Role in Systems Development

1.17

Other specialist

1.18

Database Administrator: Involved in design, development and maintenance of databases

Network and telecommunications experts: Develop systems involving data and/or voice communications

Human Factors Specialists: Involved in training users and writing documentation

Internal Auditors: Ensure that required controls are built into the system

Software Cost SW cost often larger than computer system .

SW Maintenance cost is several SW development

cost.

Nearly 60% of SW costs are development costs,

40% are testing costs.

Software products

19 Chapter 1 Introduction

Generic products

Stand-alone systems that are marketed and sold to any

customer (such as PC graphics programs, project

management tools; CAD software; ).

What the software should do is owned by the developer.

The decisions on software changes made by the developer

Customized products

Software that is specified by a specific customer to meet their

own needs such as embedded control systems, air traffic

control software, traffic monitoring systems.

What the software should do is owned by the customer.

The decisions on software changes are made by the

customer

Software process activities

Software specification: customers and engineers define the

software and the constraints on its operation

Software development: the software is designed and

programmed

Software validation: The software is checked to ensure that it

is what the customer requires

Software evolution: the software is modified to reflect

changing customer and market requirements

20 Chapter 1 Introduction

Application types

Stand-alone applications: Run on a local PC, include all

necessary functions, and no need for network connection.

Interactive transaction-based applications: Applications that

execute on a remote computer and are accessed by users from

their own PCs. (web applications such as e-commerce).

Embedded control systems: Control systems that control and

manage hardware devices.

Batch processing systems: Business systems designed to

process large numbers of individual inputs.

Entertainment systems: developed for personal use

Systems for modelling and simulation: Are developed by

scientists and engineers to model physical processes.

Data collection systems: collects data from their environment

using a set of sensors and send that data to other systems for

processing.

Types of Information Systems and Systems

Development

1.22

Transaction Processing Systems (TPS): Automate handling of data about business activities (transactions)

Management Information Systems (MIS): Converts raw data from transaction processing system into meaningful form

Decision Support Systems (DSS): Designed to help decision makers

Expert Systems (ES)

Replicates decision making process

Knowledge representation describes the way an expert would approach the problem

1.23

Software engineering ethics

Software engineering involves wider responsibilities than simply

the application of technical skills

Confidentiality: Engineers should respect the confidentiality of their employers or clients

Competence : Engineers should not misrepresent their level of competence.

Intellectual property rights: Engineers should be aware of

local laws governing the use of intellectual property such as

patents, copyright, etc.

Computer misuse: Software engineers should not use their

technical skills to misuse other people’s computers

24

Issues of professional responsibility

Confidentiality

Engineers should respect the confidentiality of their employers or clients

Competence

Engineers should not misrepresent their level of competence.

Intellectual property rights

Engineers should be aware of local laws governing the use

of intellectual property such as patents, copyright, etc.

Computer misuse

Software engineers should not use their technical skills to

misuse other people’s computers. 25 Chapter 1 Introduction

Systems Development Life Cycle

A standard set of steps,, to develop and support their

information systems.

A commercial product, such as a Nike sneaker or a Honda

car, follows a life cycle:

Ex. Honda car: created, tested, and introduced to the

market. Its sales increase, peak, and decline. Finally, the

product is removed from the market and is replaced by

something else.

Every organization uses a slightly different life-cycle model

to model these steps

1.26

Copyright 2006 Prentice-

Hall, Inc.

1.27

Phases of the SDLC

Systems Planning and Selection

Main Activities

Identification of need for enhancing the current system or for new system ( written plane of IS dept.), schedule for developing new system

A feasibility study is conducted to determine the economic and organizational impact of the system.

Investigation and determination of scope

Output:

The final presentation to the organization’s management of the plan for proceeding with the subsequent project phases is usually made by the project leader and other team members.

Phases of the SDLC

Systems Analysis the analyst studies the organization’s current procedures

and information systems used to perform tasks such as general

ledger, machine scheduling, and payroll.

Determine requirements : what the users want from a

proposed system a careful study of any current systems,

manual and computerized, that might be replaced or enhanced

as part of this project.

generate alternative initial designs to match the requirements

Compare alternatives and Recommend the best alternative

Output:

A description of the alternative solution recommended by the analysis team.

Phases of the SDLC-

System Design the recommended alternative solution into logical and then physical system specifications. input and output screens to reports, databases, and computer processes. Environment Independent ( HW and SW)

Logical Design: Concentrates on business aspects of the system

Physical Design

Technical specifications and the analyst team decides which programming languages , DBMS , HW , Operating system , Network environment

Output:

the physical system specifications presented in a form, such as a diagram or written report, ready to be turned over to programmers and other system builders for construction.

SDLC – Implementation and operation

Implementation

Coding: Write Programs the make up the system

Testing : Testing the program to find errors if exist.

Installation: Application is installed on the New HW

User is introduced to the system an trained on it

Documentation

users sometimes find problems with how it works and often think of improvements.

The amount of time and effort devoted to system enhancements during operation depends a great deal on the performance of the previous phases of SDLC.

Products of the SDLC

Alternative Approaches to Development

Prototyping

Building a scaled-down working version of the system

The analyst works with users to determine the basic

requirements for the system.

The analyst then quickly builds a prototype.

the users check it and tell the analyst what they like

and do not like about it.

The analyst uses this feedback to improve the

prototype and takes the new version back to the

users.

This iterative process continues until the users are

relatively satisfied with what they have seen.

Advantages: Users are involved in design

Alternative Approaches to Development Prototyping

Approaches to Development (continued)

Computer-Assisted Software Engineering (CASE) Tools

Automated software tools used by systems analysts to develop

information systems

Can be used throughout SDLC

Product and tool integration is provided through a repository

General types of CASE tools

• Diagramming tools

• Computer display and report generators

• Analysis tools

• Repository

• Documentation generators

• Code generators

1.35

Outsourcing

Practice of another organization developing and/or running a

computer application for your organization

Many types of working arrangements

Should be considered as one possible alternative to developing

a system

1.36

Sources of Software

What is done when a problem raised ?

When developing information systems to deal with such

problems, an organization and its systems analysts have

several options:

Go to Information Technology Services Firms, HP

Packaged Software Providers on shelf SW (Buy)

Implement Wide Enterprise Solutions Software SAP

Open-Source Software

Use In-House stuff for developing solution

Out sourcing system development and operations

1.37

Selecting Off-the-Shelf Software

Cost: comparing the cost of developing the same system in-house with the cost of purchasing or licensing the software package

Functionality: the tasks that the software can perform and the mandatory, essential, and desired system features

Vendor support: whether or how much support the vendor can provide and at what cost.

Viability of vendor: can the software adapt to changes in systems software and hardware

Flexibility: how easy it is to customize the software

Documentation: is the user’s manual and technical documentation

understandable and up-to-date

Response time: how long it takes the software package to respond to the user’s requests in an interactive session

Ease of installation: a measure of the difficulty of loading the software and making it operational

compatibility with currently used application software and HW. hardware and system software

Case studies A personal insulin pump

An embedded system in an insulin pump used by

diabetics to maintain blood glucose control

A mental health case patient management system

A system used to maintain records of people receiving

care for mental health problems

A wilderness weather station

A data collection system that collects data about

weather conditions in remote areas

39

Insulin pump control system

Collects data from a blood sugar sensor and

calculates the amount of insulin required to be injected

Calculation based on the rate of change of blood

sugar levels

Sends signals to a micro-pump to deliver the correct

dose of insulin

Safety-critical system as low blood sugars can lead to

brain malfunctioning, coma and death; high-blood

sugar levels have long-term consequences such as

eye and kidney damage

40

Insulin pump hardware architecture

41 Chapter 1 Introduction

A personal insulin pump An embedded system in an insulin pump used by

diabetics to maintain blood glucose control

Activity model of the insulin pump

42 Chapter 1 Introduction

Essential high-level requirements

The system shall be available to deliver insulin

when required.

The system shall perform reliably and deliver

the correct amount of insulin to counteract the

current level of blood sugar.

The system must therefore be designed and

implemented to ensure that the system always

meets these requirements.

43

A patient information system for mental health care

A patient information system to support mental health

care is a medical information system that maintains

information about patients suffering from mental health

problems and the treatments that they have received

Most mental health patients do not require dedicated

hospital treatment but need to attend specialist clinics

regularly where they can meet a doctor who has

detailed knowledge of their problems

To make it easier for patients to attend, these clinics

are not just run in hospitals. They may also be held in

local medical practices or community centres.

44

MHC-PMS (Mental Health Care-Patient Management System)

The MHC-PMS is an information system that is

developed for use in clinics

It makes use of a centralized database of patient

information but has also been designed to run on a

PC, so that it may be accessed and used from sites

that do not have secure network connectivity

When the local systems have secure network access,

they use patient information in the database but they

can download and use local copies of patient records

when they are disconnected

45

MHC-PMS goals

To generate management information that allows health service

managers to assess performance against local and government

targets.

To provide medical staff with timely information to support the

treatment of patients.

46 Chapter 1 Introduction

MHC-PMS key features

Individual care management : Clinicians can create

records for patients, edit the information in the system, view

patient history, etc. The system supports data summaries so

that doctors can quickly learn about the key problems and

treatments that have been prescribed.

Patient monitoring: The system monitors the records of

patients that are involved in treatment and issues warnings if

possible problems are detected

Administrative reporting: The system generates monthly

management reports showing the number of patients treated at

each clinic, the number of patients who have entered and left

the care system, number of patients sectioned, the drugs

prescribed and their costs, etc.

47

MHC-PMS concerns

Privacy

It is essential that patient information is confidential and is

never disclosed to anyone apart from authorised medical

staff and the patient themselves

Safety

Some mental illnesses cause patients to become suicidal or

a danger to other people. Wherever possible, the system

should warn medical staff about potentially suicidal or

dangerous patients.

The system must be available when needed otherwise

safety may be compromised and it may be impossible to

prescribe the correct medication to patients

48

Wilderness weather station

The government of a country with large areas of

wilderness decides to deploy several hundred weather

stations in remote areas.

Weather stations collect data from a set of instruments

that measure temperature and pressure, sunshine,

rainfall, wind speed and wind direction.

The weather station includes a number of instruments

that measure weather parameters such as the wind

speed and direction, the ground and air temperatures,.

Each of these instruments is controlled by a software

system that takes parameter readings periodically and

manages the data collected from the instruments.

49

The weather station’s environment

50 Chapter 1 Introduction

The weather station system: Is responsible for collecting

weather data, carrying out some initial data processing and

transmitting it to the data management system.

The data management and archiving system: collect the

data from all of the wilderness weather stations, process,

analyse and archives the data.

The station maintenance system: communicate by satellite

with all wilderness weather stations to monitor the health of

these systems and provide reports

Additional software functionality

Monitor the instruments, power and communication

hardware and report faults to the management

system.

Manage the system power, ensuring that batteries are

charged whenever the environmental conditions

permit but also that generators are shut down in

potentially damaging weather conditions, such as high

wind.

Support dynamic reconfiguration where parts of the

software are replaced with new versions and where

backup instruments are switched into the system in

the event of system failure.

51

Questions 1. What is the information systems analysis and design?

2. What is meant by the system, list the main characteristics of the system?

3. What is meant by methodology , Tools , Techniques?

4. What is decomposition? Coupling? Cohesion?

5. In what way are organizations systems?

6. Describe the major Types of Information systems?

7. What is meant by outsourcing? And what are the main sources of software?

8. What is the main role of the analyst? And what are the skills that must be achieved in the system analysis?

9. List and explain the different phases in the systems development life cycle.

10.What is prototyping?

11.What are CASE tools? What is a CASE repository and how is it used?

52

Questions

12.How can you decide among various off-the shelf software options? What criteria should you use?

13.Explain why professional software is not just the programs that are developed for a customer.

14.What is the most important difference between generic software product development and custom software development? What might this mean in practice for users of generic software products?

15.What are the four important attributes that all professional software should have? Suggest four other attributes that may sometimes be significant.

16. Apart from the challenges of heterogeneity, business and social change, and trust and security, identify other problems and challenges that software engineering is likely to face in the 21st century (Hint: think about the

environment). 53