TCS 2411 Software Engineering

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System Engineering and

Analysis

“What is the role of the software product?”

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Lecture Objectives

To examine the elements of a computerbased system

To understand the development process of a system

To illustrate the representations of a business information system

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Definition of System

“A collection of interrelated components that work together to achieve some objective”

Objective: to develop a product, to support business functions…etc

.

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Information system types

Manual (read a text by your eyes then summarize using your pen)

Automated (get the information through a computerized system)

Process

Information

Data

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system environments

Internal, like users, organization structure and procedures

External, consists of all factors outside the organization that affect the system

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System Elements

Software: computer programs, data structures, and related documents.

Hardware: electronic computing devices and connectivity devices.

People: users and operators.

Database: large and organized collection of information that is accessed via the software.

Documentation: descriptive information for user and operator (e.g. hardcopy manuals, on-line help files)

Procedures: steps that define the specific use of each system element.

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System Life Cycle

Phases

Initial Strategy

Identification of needs, problems, opportunities, goal objectives and scope.

Critical to the success of the project.

The analyst must be honest.

The analyst must discover what the business is trying to do

.

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System Life Cycle

Phases

(Continued)

Determining the Requirements

(Information and Tools)

Several tools are used to define IR in the business, sampling, investigating of hard data, interviewing, questionnaires, observing, prototyping.

The analyst is striving to understand what information users need to perform their job

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System Life Cycle

Phases

(Continued)

Feasibility Study

Economic, technical, legal feasibility

(can be done or not).

Cost-benefit analysis, risk assessment

"Go / no-go" decision

Analysis

Requirements definition & specification there are some special tools and techniques that help the analyst as DFD, Data Dictionary

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System Life Cycle

Phases

(Continued)

Design

Logical & Physical Design (Design the interface, input/output, file or database)

System specifications

Implementation

Installation

Training

File conversion

Systems testing, security

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System Life Cycle

Phases

(Continued)

Maintenance, Review and Test

Amendments (fix) by the programmers

System audit, by the programmers and analyst

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Domain of interest

System element

System Engineering

Hierarchy

Business or product domain

World view

Domain view

Element view

Detailed view

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System Engineering

Hierarchy continue

World view: the entire business or technology is examined.

Domain view: specific domain of interest.

Element view: the need for targeted system element (e.g. data, software, hardware, people) is analyzed.

Detailed view: analysis, design, and construction of a targeted system element.

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System Modeling

The engineer creates models that:

 define processes for the view under consideration.

 represent behaviour of the processes

 explicitly define endogenous exogenous and input to the model

 represent all linkages (including output) to better understand the view

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Exogenous &

Endogenous Inputs

Exogenous inputs link one constituent of a view with other constituents (at the same or other levels)

Endogenous inputs link individual components of a constituent at a particular view

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Restraining Factors of

System Model

Assumptions

Simplifications

Limitations

Constraints

Preferences

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Enterprise Modeling

Organizational structure

Business-level data modeling

Process modeling

Information flow modeling

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Organizational

Structure

XYZ

Company

Corporate

Support

Finance

Sales &

Marketing

Engineering

…..

Manufacturing

Planning

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Business-level Data

Modeling

Product A describes sells

Salesperson purchases evaluates inquires about

Customer

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Process Modeling

Establish customer contact

Provide evaluation product

Provide product info

Address questions/ concerns

Check availability

Prepare delivery order

Accept sales order

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Information Flow

Modeling

Contact record

Product description

Establish customer contact

Provide evaluation product

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Product info

Provide product info

Customer

Prepare delivery order d.o. info

Address questions/ concerns queries order

Check availability

Accept sales order configuration availability

Inventory

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Summary

System analysis provides the ‘big’ picture of the computer-based system where software is to be used

By understanding the system, a better software product can be produced

Identification of elements of the system provides the framework for software requirements

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Software Requirements

Specifications

Problem Statement

 system reference, problem areas

Data model

Entity Relationship Diagram

Functional requirements

List of functions, Context diagram, DFD

Behaviour model

State Transition Diagram

Glossary of Terms

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References

“Software Engineering: A Practitioner’s

Approach” 5th Ed. by Roger S. Pressman,

Mc-Graw-Hill, 2001

“Software Engineering” by Ian Sommerville,

Addison-Wesley, 2001

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