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