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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”