Modern Systems Analysisand Design

Third Edition

Chapter 11Selecting the Best Alternative

Design Strategy

11.111.1

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

11.211.2

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

11.311.3

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

11.411.4

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

11.511.5

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

11.611.6

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

11.711.7

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

11.811.8

11.911.9

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

11.1011.10

Criteria for Choosing Off-the-Shelf Software

• Flexibility– Ease of customization

• Documentation– User documentation– Technical documentation

• Response Time• Ease of Installation

11.1111.11

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

11.1211.12

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

11.1311.13

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

11.1411.14

Hoosier Burger’s New Inventory Control System

• Replacement for existing system• Figure 11-2 ranks system requirements and

constraints• Figure 11-3 shows steps of current system• When proposing alternatives, the

requirements and constraints must be considered

11.1511.15

Hoosier Burger’s New Inventory Control System

• Figure 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

11.1611.16

Hoosier Burger’s New Inventory Control System

• Selecting 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

11.1711.17

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

11.1811.18

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

11.1911.19

Internet Development: Selecting the Best Alternative Design Strategy

• Pine Valley Furniture WebStore– Requirements and constraints were compiled by

consultant and team (see Table 11-8)

11.2011.20

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 infrastructure

11.2111.21