Transcript TCS 2411 Software Engineering

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
Data
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Information
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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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System Engineering
Hierarchy
Domain of
interest
System
element
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 exogenous and
endogenous 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
Sales &
Marketing
Engineering
Manufacturing
…..
Finance
Planning
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Business-level Data
Modeling
Product A
describes
sells
Salesperson
purchases
evaluates
inquires about
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contacts
Customer
assists
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Process Modeling
Establish
customer
contact
Provide
evaluation
product
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Prepare
delivery
order
Provide
product
info
Address
questions/
concerns
Check
availability
Accept
sales
order
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Information Flow
Modeling
Contact record
Establish
customer
contact
Product
description
Provide
evaluation
product
Prepare
delivery
order
Product
info
Provide
product
info
Customer
Check
availability
queries
Address
questions/
concerns
d.o. info
order
availability
Accept
sales
order
Inventory
configuration
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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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