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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