Copyright 2002 Prentice-Hall, Inc.

Modern Systems Analysisand Design

Third Edition

Jeffrey A. Hoffer Joey F. George

Joseph S. Valacich

Chapter 11Selecting the Best Alternative

Design Strategy

11.1

Learning Objectives

Describe different sources of softwareLearn to assemble the various pieces of

an alternative design strategyLearn how to generate at least three

alternative design strategiesDiscuss selecting the best design

strategy using both qualitative and quantitative methods

11.2

Learning Objectives

Learn how to use the results of the analysis phase to update a Baseline Project Plan (BPP)

Discuss design strategies and how they are applied to the Internet

11.3

Selecting the Best Alternative Design Strategy

Two basic steps1. Generate a comprehensive set of alternative design

strategies2. Select the one design strategy that is most likely to result in

the desired information system

Process Divide requirements into different sets of capabilities Enumerate different potential implementation environments

that could be used to deliver the different sets of capabilities

Propose different ways to source or acquire the various sets of capabilities for the different implementation environments

11.4

Selecting the Best Alternative Design Strategy

Deliverables1. At least three substantially different system

design strategies for building the replacement information system

2. A design strategy judged most likely to lead to the most desirable information system

3. A Baseline Project Plan (BPP) for turning the most likely design strategy into a working information system

11.5

Generating Alternative Design Strategies

Best to generate three alternatives Low-end

Provides all required functionality users demand with a system that is minimally different from the current system

High-end Solves problem in question and provides many

extra features users desire Midrange

Compromise of features of high-end alternative with frugality of low-end alternative

11.6

Drawing Bounds on Alternative Designs

Minimum Requirements Mandatory features versus desired

features Forms of features

Data Outputs Analyses User expectations on accessibility,response

time and turnaround time

11.7

Drawing Bounds on Alternative Designs

Constraints on System Development Date when system is needed Financial and human resources Elements of the system that cannot change Legal and contractual considerations Dynamics of the problem

11.8

Issues to Consider in Generating Alternatives

Outsourcing The practice of turning over responsibility

of some to all of an organization’s information systems applications and operations to an outside firm

Can provide a cost effective solution

11.9

Issues to Consider in Generating Alternatives

Sources of Software Hardware manufacturers Packaged software producers Custom software producers Enterprise solution software Application Service Providers In-house development

11.10

11.11

Criteria for Choosing Off-the-Shelf Software

Cost In-House versus purchased

Functionality Mandatory, essential and desired features

Vendor Support Installation Training Technical Support

Viability of Vendor

11.12

Criteria for Choosing Off-the-Shelf Software

Flexibility Ease of customization

Documentation User documentation Technical documentation

Response Time

Ease of Installation

11.13

Validating Purchased Software Information

Information from vendor Request for proposal

A document provided to vendors to ask them to propose hardware and system software that will meet the requirements of your new system

Software evaluation period

Customer references from vendor

Independent software testing service

Trade publications

11.14

Hardware and Software Issues

Existing Platform1. Lower costs2. Information system staff

is familiar with operation and maintenance

3. Increased odds of successfully integrating system with existing applications

4. No added costs of converting old systems to new platform or transferring data

New Hardware and System Software1. Some software

components will only run on new platform

2. Developing system for new platform gives organization opportunity to upgrade technology holdings

3. New requirements may allow organization to radically change its computing operations

11.15

Implementation and Organizational Issues

Implementation Issues Technical and social aspects of implementation

need to be addressed Training Disruption of work

Organizational Issues Overall cost and availability of funding Management support User acceptance

11.16

Hoosier Burger’s New Inventory Control System

Replacement for existing systemFigure 11-2 ranks system requirements and constraintsFigure 11-3 shows steps of current systemWhen proposing alternatives, the requirements and constraints must be considered

11.17

Hoosier Burger’s New Inventory Control SystemFigure 11-4 lists 3 alternatives Alternative A is a low-end proposal Alternative C is a high-end proposal Alternative B is a midrange proposal

11.18

Hoosier Burger’s New Inventory Control SystemSelecting the most likely alternative Weighted approach can be used to compare the

three alternatives Figure 11-5 shows a weighted approach for

Hoosier Burger Left hand side of table contains decision criteria

Constants and requirements Weights are arrived at by discussion with analysis team,

users and managers Each requirement and constraint is ranked

1 indicates that the alternative does not match the request well or that it violates the constraint

5 indicates that the alternative meets or exceeds requirements or clearly abides by the constraint

11.19

Hoosier Burger’s New Inventory Control System

Selecting the most likely alternative According to the weights used, alternative

C appears to be the best choice

11.20

Updating the Baseline Project Plan (BPP)

The Baseline Project Plan (BPP) was developed during project initiation and planning

Baseline Project Plan (BPP) can be used as an outline of a status report at analysis phase

Schedule will be updated to reflect actual activities and durations

An oral presentation of project status is typically made at this phase

11.21

Internet Development: Selecting the Best Alternative Design

StrategyPine Valley Furniture WebStore Requirements and constraints were

compiled by consultant and team (see Table 11-8)

11.22

Internet Development: Selecting the Best Alternative Design

Strategy Proposed system is a scalable, three-tier

approach Scalable

The ability to seamlessly upgrade the system through either hardware upgrades, software upgrades or both

Three-tier Web Server

Provides connection to the internet and presentation of HTML page

Applications Server Middle layer of software and hardware that lies

between Web server and corporate network Corporate network

Existing organizational computing infrastructure11.23

Summary

Sources of Software

Identifying requirements and constraints

Generating alternative design strategies

Selecting the best design strategy

Updating a Baseline Project Plan (BPP)

Selecting the best design strategy for Internet applications

11.24