Transcript Data Modelling – ERD’s

Information Systems in Organisations
System Development: The Environment
IT Systems Analysis and Design
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a method used by companies to create and maintain
information systems that perform basic business
functions
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main goal is to improve organisational systems
SAD (Core Concepts)
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analysis and design process usually involves developing or
acquiring application software, which is designed to
support a specific organizational function or process.
Methodologies & Techniques
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methodology is a sequence of step-by-step approaches
that help develop the information system
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techniques are processes that need to be followed to
help ensure that the work is complete and
comprehensible
Tools
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computer programs such as computer-aided software
engineering (CASE) tools, that make it easy to use specific
techniques
What is a system?
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A group of interrelated procedures used for a business
function, with an identifiable boundary, working together
for same purpose.
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examples – payroll system, inventory system, student
registration system
System Characteristics
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Components/interrelated components
Boundary
Purpose
Environment
Interfaces
Input
Output
Constraints
System Characteristics
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An irreducible part or aggregation of parts that makes
up a system (also called a subsystem)
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Interrelated component – the function of one
component is somehow tied to the function of others
(e.g. customer records need to be sorted before a
report is produced)
System Characteristics Boundary
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The line that marks the inside and outside of a system
and that sets off one system from another system
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Systems outside the boundary cannot be changed – e.g.
a customer system will be for customers only and not
include the public
Purpose & Environment
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The overall goal or function of a system
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Environment – everything external to the system that
interacts with the system
Interface and Constraint
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Interface – point of contact where a system meets its
environment or where subsystems meet each other.
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Constraint – a limit to what a system can accomplish
System Concepts
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Decomposition – the process of breaking the
system into smaller components (which in turn can be
broken down as well)
Modularity – dividing a system into modules of equal
size
Coupling – the extent to which the systems depend
on each other
Cohesion – the extent to which a subsystem
performs a single function.
System Analyst
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Person most responsible for the analysis and design of
information systems
Primary role is to study the problems and needs of the
organization in order to bring about improvements
Person needs to possess analytical, technical, managerial
and interpersonal skills
Categories of ISs
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Transaction processing systems
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Management information systems
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Decision support systems
Transaction Processing System
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TPS automates the handling of data about business
activities and transactions
(high volume/data capture focus)
Examples – supermarket cash register, bank machines,
retailer POS
Goal is to processing up and improve efficiency and
accuracy
Process orientation
Management Information System
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MIS is a computer based system that takes the raw data
available through a TPS and converts it into a meaningful
aggregated form.
Examples sales reports – which items sell well and which
are slow selling items.
Data orientation – understand relationships between data
Decision Support System
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DSS is designed to help decision makers with decisions.
It allows people making the decisions to quickly manipulate
data
What if analysis
Usually DSSs are used by higher management
Data and decision logic orientation
System Development Methodology
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A standard process followed by organization to conduct all
the steps necessary to analyze, design, implement and
maintain information systems
Systems Development Life Cycle (SDLC) is a commonly
used methodology
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Planning and selection
Analysis
Design
Implementation and Operation
SDLC (Planning & Selection)
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An organization’s total IS needs are analyzed and
A potential IS project is identified and decision is made
whether the project will continue or not
A feasibility study is conducted
Investigation of the system’s
scope is also determined
SDLC (System Analysis)
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The current system is studied and alternative replacement
systems are proposed
System requirements are determined (e.g. user needs!)
Alternative solutions are recommended
SDLC (System Design)
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The chosen system (to be developed) is described
independently of any computer platform (logical design)
Then transformed into technology-specific details (physical
design) from which all programming and system
construction can be accomplished
SDLC (Implementation & Operation)
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Information system is coded, tested and installed in the
organization
Information system is systematically repaired and improved
System specifications are turned into a working system that
is tested and then put into use!
Even a well designed system can fail if implementation is not
managed well!
Approaches to Development
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Prototyping
Computer-aided software engineering (CASE)
Joint application design (JAD)
Rapid Application Development (RAD)
Participatory design
Agile Methodologies
References
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Essentials of Systems Analysis and Design
(Pearson International) 4th Edition
Valacich, George and Hoffer, Chapter 1