Chapter 6

Systems Design

• The design stage in the SDLC

• Evolution in IS design

• Evolution in computer architectures

• The systems approach to design

• User interface design

• Data design

• Procedure design

• Software design

• System interface design

• System control design

• Quantitative evaluation of design alternatives

• Information infrastructure design

The Design Stage in the SDLC

Fig 6.1: Design Phase Overview

Evolution in IS design

1. Document preparation

2. Organizational problem solving

3. Organizational database

4. Enterprise data model

• ERDs

• Data dictionary

• Object models

Two basic types of design

• Logical

• Physical

Evolution in Computer Architectures

Fig 6.2: The Evolution in Computer Architectures

Evolution in Computer Architectures

Mainframe computing

Fig 6.3: Mainframe Computing

Evolution in Computer Architectures

Client/server computing

Fig 6.4: Client/Server Computing

Evolution in Computer Architectures

Client/server environments

Fig 6.5: Range of Application Partitioning for Web-Based Distributed-Object Computing

Web-based distributed object computing

The Systems Approach to Design

• Identify alternate designs

• Evaluate alternate designs

• Select the best

The Systems Approach to Design

Identify alternate designs

• Use system components

Fig 6.6: System Design Efforts

The Systems Approach to Design

Evaluate alternate designs

Fig 6.7: Five Types of Design Performed on Each Configuration of a Sample Module

Select the best

User Interface Design

Input design

• Types of input devices

• Source document design tips

Natural forms completion pattern

Right size fields

Carbon sets

Fit envelopes

Test before printing

User Interface Design

Output design

• Reports

Fig 6.8: Types of Reports

User Interface Design

Tabular report design tips

• Use layout forms

• Complete identifying information

• Management by exception

User Interface Design

Graphical reports

Fig 6.10: Sample Graphic Report Formats

User Interface Design

Graphical reports design tips

• Line and bar charts to summarize, show trends

• Grouped bar to illustrate parts of a whole (versus pie charts)

• Grouped line and bar to show patterns (versus segmented charts)

• Use horizontal bars with data values at the ends

Data Design

Data modeling approach

• ERD

• Data Dictionary

Object modeling approach

• Object class diagram

Procedure Design

Batch processing

Online processing

Realtime processing

Procedure Design

Batch processing

Fig 6.11: Batch Processing

Procedure Design

Online processing

Fig 6.12: Online Processing

Realtime processing

Software Design

Strategies

• Make the client/server decision

• Adhere to strict naming conventions, path rules, and relative links

• Limit modules to simple routines

• Create templates and class libraries

• Enforce programming principles

Software Design

ASTA input/output standards

Fig CS 3.5: Standards Input/Output

Software Design

ASTA programming standards

Fig CS 3.6: Programming Standards

System Interface Design

Use Figure 0 DFDs

Fig 6.13: The Distribution System

System Control Design

Design controls to address risks

• Risk and control matrices

Build controls into each system element

System Control Design

Risk matrix

Fig 6.14: A Risk Matrix

System Control Design

Control Matrix

Fig 6.15: A Control Matrix

System Control Design

System elements

Fig 6.16: Controls Are Designed into System Elements

Quantitative Evaluation of Design Alternatives

Fig 6.17: A Quantitative Approach to the Evaluation of a Possible Solution

Information Infrastructure Design

AIS

• Accounting fundamentals

• Information needs of environmental elements

• Database design

The enterprise systems (support business functions) – MIS, DSS, knowledge-based systems

• Organization structure

• Management functions and roles

• Periodic report design

• Database design

• Math modeling

• Group dynamics