Chapter 9: Basic Information Systems Concepts

Definitions

A system is a set of interrelated components that must work together to achieve some common purpose.

A subsystem is a component of a system which is also viewed as a system.

Definitions

An information system is a collection of computer hardware and software, procedures, documentation, forms, and people responsible for the capture, movement, management, and distribution of data and information.

System Boundary

Dividing line Placed based on the purpose --

usually not a fixed line Control or redesign within the

boundary Environment outside the boundary

Environment

Input 2

Input 1

Output 1

Boundary

Interface

Interface

Interface

System

Component 1

Component 3

Component 2

Storage 1

System Interface

Where a system meets its environment or where one subsystem interacts with another subsystem

Code/decode and filter Error detection and correction Hold/buffer Security and validate/reject Provides decoupling of components

Hierarchical Decomposition

Factor systems into subsystems Examine interfaces Keep going deeper until

subsubsystems are understandable Uses -- analysis and design Purposes -- cope with complexity,

communication, identification of interfaces, seek decoupling

Definition of Business Process Reengineering

Hammer & Champy’s quick definition: “starting over.”

Hammer & Champy’s full definition: “Reengineering is the fundamental rethinking and radical redesign of business processes to achieve dramatic improvements in critical, contemporary measures of performance.”

Business Process Reengineering

Information technology is the essential enabler which permits companies to reengineer business processes.

Businesses must take advantage of the disruptive power of technology.

In the U.S., there have been great savings, but also tremendous costs in terms of jobs and people.

Revised Definition of BPR

Business process reengineering is the radical redesign of business processes to achieve dramatic improvements in their performance by taking advantage of information technology.

radical -- dramatic -- processes -- information technology

Commonalities in Successful BPR Efforts

Several jobs are combined into one.

Workers make decisions. The steps in the process are

performed in a natural order. Work is performed where it makes

the most sense.

Commonalities in Successful BPR Efforts (continued)

Checks and controls are reduced, and reconciliation is minimized.

Hybrid centralized/decentralized operations are prevalent.

Using Information Technology to Break Dysfunctional Rules

Old rule: Information can appear in only one place at one time.

Disruptive technology: Shared databases

New rule: Information can be used simultaneously in many places.

Example #1

Using Information Technology to Break Dysfunctional Rules

Old rule: Only EXPERTS do complex work.

Disruptive technology: Expert systems

New rule: Generalists can do complex work like an EXPERT.

Example #2

Using Information Technology to Break Dysfunctional Rules

Old rule: Field personnel need OFFICES to receive, store, retrieve, and transmit information.

Disruptive technology: Portable and home computers, modems, and wireless data communication

New rule: Field personnel send and receive info. WHEREVER they are.

Example #3

The Information Systems Life Cycle

Definition phase

Construction phase

Implementation phase

IS Development: Procedural-Oriented Techniques

Documenting the existing system: the As-Is model

Creating a model of the desired future system: the Logical To-Be model

Interpreting the logical model as a physical system design: the Physical To-Be model

Tools for the As-Is Model

Describe what you have NOW! Context diagram (see example) Work process flow diagram (see

example)

Tools for the Logical To-Be Model

Define WHAT you want the new system to do! (Not how it will be done)

Data flow diagram (see example) Data dictionary Entity-relationship diagram (see

example)

Tools for the Physical To-Be System

Describe HOW the new system will operate!

Program structure chart (see example)

Input form layout Report layout

IS Development: Object-Oriented Techniques

Key idea: Work with reusable objects to speed up development!

TWO PRINCIPLES: Storing data and related operations

together within objects (encapsulation)

Sharing commonalities between classes of objects (inheritance)

Why Controls?

Assess the quality of performance of the IS function

Control criminal activity

Prevent destruction of data or equipment

Reduce errors

Controls in Information Systems

Backup and recovery Methodology standards Edit rules Security EDP auditing System testing Control calculations

Examples of Controls

Authorization of system development by top management

Corporate data access policy Separation of duties Physical controls for data center Scrutiny of computer logs “Firewalls”