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Information Systems in Organisations
System Development: The Environment
IT Systems Analysis and Design
a method used by companies to create and maintain information systems that perform basic business functions
main goal is to improve organisational systems
SAD (Core Concepts) analysis and design process usually involves
developing or acquiring application software, which is designed to support a specific organizational function or process.
Methodologies & Techniques
methodology is a sequence of step-by-step approaches that help develop the information system
techniques are processes that need to be followed to help ensure that the work is complete and comprehensible
Tools
computer programs such as computer-aided software engineering (CASE) tools, that make it easy to use specific techniques
What is a system?
A group of interrelated procedures used for a business function, with an identifiable boundary, working together for same purpose.
examples – payroll system, inventory system, student registration system
System Characteristics
Components/interrelated components Boundary Purpose Environment Interfaces Input Output Constraints
System Characteristics
An irreducible part or aggregation of parts that makes up a system (also called a subsystem)
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
The line that marks the inside and outside of a system and that sets off one system from another system
Systems outside the boundary cannot be changed – e.g. a customer system will be for customers only and not include the public
Purpose & Environment
The overall goal or function of a system
Environment – everything external to the system that interacts with the system
Interface and Constraint
Interface – point of contact where a system meets its environment or where subsystems meet each other.
Constraint – a limit to what a system can accomplish
System Concepts
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
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
Transaction processing systems
Management information systems
Decision support systems
Transaction Processing System
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
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 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 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 Planning and selection Analysis Design Implementation and Operation
SDLC (Planning & Selection) 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) 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) 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)
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 Prototyping Computer-aided software engineering (CASE) Joint application design (JAD) Rapid Application Development (RAD) Participatory design Agile Methodologies
References
Essentials of Systems Analysis and Design(Pearson International) 4th EditionValacich, George and Hoffer, Chapter 1