Acca 11(information systemsdevelopmentprocess)

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Information Systems
Development Process
Lecture 11
Abdisalam Issa-Salwe
Faculty of Professional Studies
Thames Valley University

Abdisalam Issa-Salwe, Thames Valley University
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Topic list
 System development lifecycle
 The Waterfall Model
 The Spiral Model
 Systems development
methodologies
 Software support for the systems
development process
 User involvement

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System development cycle
 In early days of computing, systems
were developed in fairly haphazard way
resulting in poorly designed systems
which were too expensive and were not
suited to the user’s needs
 In the 1960s, the National Computing
Centre developed a more disciplined
approach to systems development
which was applicable almost
everywhere

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System development cycle (cont…)
This approach was called the Systems
Development Lifecycle and contained
the following stages:
 Feasibility Study
 Systems Investigation
 Systems Analysis
 Systems Design
 Implementation
 Review and Maintenance

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 System development life-cycle
was developed to add discipline
to many organisations’ approach
to systems development.
 Systems development lifecycle is
the process of conceiving,
designing and implementing an
information system.

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 The Systems Development Life
Cycle (SDLC) is a framework for
describing the phases involved in
developing and maintaining
information systems
 Typical SDLC phases include
planning, analysis, design,
implementation, and support

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Systems View
 Systems approach emerged in 1950s
 more analytical approach to management &
problem solving
 Three parts:
 Systems philosophy: View things as systems,
interacting components working within an
environment to fulfill some purpose
 Systems analysis: problem-solving approach
 Systems management: Address business,
technological & organizational issues before
making changes to systems

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Drawbacks of the systems development
 Insufficient emphasis on information
needs
 Sequential, inflexible approach
 Poor documentation
 Dissatisfied users
 Users’ requirements poorly defined

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Drawbacks of the systems development (cont…)
 As information systems grow in size and
complexity, these problems may only get
worse.
 The best way to start approaching these
problems is by studying them in more
detail.
 Legacy Systems
 Increasing Systems Complexity
 Organisational Issues

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 The IS function has a poor reputation.
 Despite huge investments in information
technology:
 Systems development often takes more time
and resources than planned
 Information systems do not provide the
information needed or in the needed form
 Information systems break down too often

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 Birrell and Ould [Birrell and Ould,
1985], describe the "b-Model“:
 The b-Model recognises that the
maintenance phase of the software life-
cycle is seldom just fixing errors.
 If a software product exists for any
period of time, "maintenance" almost
always involves enhancements.
 After a while, the "maintenance phase"
of a software product looks very much
like the "development phase."

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SSADM
 SSADM (Structured Systems Analysis
and Design)
Originally designed for the UK Civil
Service.
Data driven – concentration on the
data rather than processes.
Highly structured with rules,
guidelines and standards
Documentation is crucial to all
aspects of the system project
development

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SSADM states
 Stage 0 – Feasibility Study
 Stage 1 – Investigation of Current
Environment
 Stage 2 - Business Systems Options
 Stage 3 – Definitions of requirements
 Stage 4 – Technical Systems Options
 Stage 5 – Logical Design
 Stage 6 – Physical Design

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Computer-Aided Software Engineering Tools (CASE)
 Software tools providing automated
support for systems development
 Project dictionary/workbook:
system description and
specifications
 Diagramming tools
 Example products: Oracle Designer,
Rational Rose

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CASE Tools (cont…)
 Select - Select
 Visio 2000 – Microsoft
 Visible Analyst - Visible Systems
 ER/Studio - Embarcadero
 ERWin - Computer Associates
 Oracle Designer - Oracle
 Power Designer - Sybase

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CASE Features
 Diagrams
 Documentation
 Data Dictionary
 Team Coordination
 Prototyping
 Code Generation
 Reverse Engineering

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CASE Types
 Full development - integrated
 iCASE
 Analysis & Design
 upper CASE
 Implementation & Maintenance
 lower CASE

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CASE Repository
 Data dictionary - data element
definitions and descriptions
 Ensures consistency
 Repository is much more
 Database with linkages for all system
development products and activities
 Integration
 Even across different CASE tools

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System Development Methodologies
 System Development
Methodologies - Refer to tools
and techniques used to complete
tasks of various phases.
We may use structured design
technique to design computer
programs; the technique would be
a methodology where as system
design is a phase of the life cycle

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System Development Methodologies (cont…)
 A system development methodology is a
guidelines to follow for completing every
activity in the SDLC, including specific
models, tools and techniques.
 Some methodologies are very formal, and
contain direct instruction. Everything is
defined, including the view of
documentation and content of reports.
 Other methodologies are much more
informal – just general description of
what should be done.

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System Development Methodologies (cont…)
 Different types of system development
methodologies are used in designing
information system.
 Depending upon the actual requirement
of the system, different approaches for
data processing are adopted. However,
some system groups recommends the
Centralised data processing system while
others may go in for distributed data
processing system.

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Model
 A model is a representation of some
aspect of the real world. A model may be:
 physical (like a model of an airplane) or
 abstract (e.g. in form of mathematical notation
or in graphical form).
 Most models, used in system development, are
graphical (diagrams and charts). They include
representations of inputs, outputs, processes,
data, objects, object interactions, locations,
networks, devices, or highlighting the tasks for
the project

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Tools
 A tool is a software support that helps
create models or other components
required in the project. A list of tool types
includes:
 Project management application
 Drawing/graphics application
 Word processor/text editor
 Computer-aided system engineering (CASE)
tools
 Integrated development environment (IDE)
 Database management application
 Reverse-engineering tool
 Code generator tool

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Technique
 A technique is a collection of
guidelines that help the analyst
complete a system development
activity or task.
 It might be step-by-step
instructions or more general
advices.

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Technique (cont…)
 Strategic planning techniques
 Project management techniques
 User interviewing techniques
 Data-modeling techniques
 Relational database design techniques
 Structured analysis technique
 Structured programming technique
 Software-testing techniques (e.g.
usability testing)
 Object-oriented analysis and design
techniques

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Computer Generation
 First generation: machine language
 Second generation: assembly language
 Third generation: high-level
programming languages, such as C, C+
+, and Java.
 Fourth Generation
 fifth generation: languages used for
artificial intelligence and neural
networks.

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Machine language (1GLs)
The lowest-level programming language
(except for computers that utilise
programmable microcode)
 Machine languages are the only
languages understood by computers.
 While easily understood by computers,
machine languages are almost
impossible for humans to use because
they consist entirely of numbers

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Assembly language (2GLs)
 A programming language that is once
removed from a computer's machine
language.
 Machine languages consist entirely of
numbers and are almost impossible for
humans to read and write.
 An assembly language contains the same
instructions as a machine language, but the
instructions and variables have names
instead of being just numbers.

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Fourth-Generation Languages (4GLs)
 Often abbreviated 4GL, fourth-
generation languages are
programming languages closer to
human languages than typical high-
level programming languages. Most
4GLs are used to access databases.
For example, a typical 4GL
command is:
 FIND ALL RECORDS WHERE NAME IS
"SMITH"

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5GLs
 Fifth generation: languages used for
artificial intelligence and neural
networks.
 the branch of computer science
concerned with machine behave like
humans. Example:
 Game playing
 Neutral network
 Robotics,
 Etc.

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User involvement
• User involvement focuses the needs
and wishes of users, i.e. crucial
information that must be incorporated
into the design process to ensure user
acceptance.
• To begins by classifying the users of a
product into several distinct user
groups.
• Groups then examined using methods
such as in-person interviews, group
interviews.

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User involvement
Walkthroughs: Walkthroughs investigate
how a product is used in its actual
usage environment and what are
expectations and wishes of users
concerning the product. In an
unstructured walkthrough the user is
allowed to freely demonstrate her way
of using the product, while in a
structured walkthrough the user is
asked to perform specific tasks.

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