The Prototyping Approach
Techniques for prototype
application
Types of Information
Systems
Sprague & Watson, DSS for Management, Prentice Hall, 1996
Type I (Procedure)
• High volume
• Low transaction cost
• Well structured
• Measurable
• Process & efficiency
• Data
• Clerical
Type II (Goal)
• Low volume
• High trans. value
• Poorly structured
• Hard to measure
• Goal & effectiveness
• Concepts
• Mgrs, professionals
IS Development
Approaches
• Systems Development Life Cycle
• Information Center (DSS)
• Object and Component
Type I
Large Systems
•
•
•
•
•
Intercommunications among applications
Formal methodologies
CASE technologies
Purchased products
Outsourcing
Type I
SDLC
•
•
•
•
•
Type I systems
Large and Costly
Cost justified
Formal stages of evaluation
Stages carefully reviewed and formally
approved
• Data, Process, Communications
Type II
Information Center (DSS)
•
•
•
•
•
Type II systems
Relatively small and inexpensive
Value justified
Prototyping and evolutionary design
Data, Dialog, Model
Prototyping
“It is easier to tell what you don’t like
about an existing system than to describe
what you would like in an imaginary one”
A.M. Jenkins, 1983
Choice
Life Cycle
 Prespecification
possible
 Changes expensive
 Good project
communication
 Static model OK
 Rigorous approach
useful
 Iteration unacceptable
Prototype
 Prespecification
difficult
 Quick tools work
 Communications gap
 Animated model
needed
 Rigor after
requirements
 Iteration accepted
The Prototyping Process
Identify
Initial
Requirements
Develop
System
Use and
Evaluate
Document and Install
Iterate
Prototyping Life Cycle
Determine suitability for prototyping
Identify basic needs
Develop working model
Demonstrate and solicit refinements
Revise and redemonstrate
Clean up and document
Assumptions
All requirements cannot be specified
Quick build tools are available
Communications gap between builders
and users
Active models are required
Rigorous approaches are appropriate
once requirements are known
Iteration is valuable
Use Prototyping If
Life cycle too slow
Scope of project manageable
30 screens
Small team: 1-2 users/designers
50 attributes
User not sure of specifications
User satisfaction very important
Reporting or DSS
Irregular or infrequent use
Do Not Use Prototyping If
Don’t understand tools
Data not well managed
Software not well managed
Professional staff not available
Technology response not adequate
User not willing to invest time
Factors Favoring
Prototyping
Structure: interactive, on-line (OLAP)
Logic: structured but not algorithmic
DSS applications are often data-report types
User: competent and active participant
Time Constraint: not a crash project
Management: willing to work with method
Size: not overly large or complex
Factors Favoring
Prototyping
Problem:
imprecise specifications,
poorly defined communications,
interactive model needed
Why not use prototyping
Roles
Responsible for business
solutions
Intermediary Run system for user
Builder
Write code for application
Technical Supports the development
Support
tools
Toolsmith
Build basic tool modules (often
work for software houses)
User
Requirements for Successful
Prototyping: User
Initiate the process
Seeks IS assistance
Competent in business area
Willing to spend time with system
Requirements for Successful
Prototyping: Builder
Assigned to Prototyping
Competent with tools
Knows organizational data resources
Requirements for Successful
Prototyping: Technology
Roles identified
4GL Tools established
Data is managed
Technology response adequate
Builders Added Value
(Professional Design)
Date and time stamps
Control totals
Audit trails
Common interface feel
Additional functions
Testing
Prototyping Principles
1. Most applications arise from a small set
of basic systems
1.
2.
3.
4.
5.
6.
Batch edit/update 7. On-line application
Batch reporting
interface
Batch data update 8. On-line report
Batch interface
On-line update/query
On-line ad hoc query
Prototyping Principles
2. Most systems use a common set of
data processing functions
Add
Modify
Display
Delete
Locate
Browse
Activate
Copy
Connect
Stop
Prototyping Principles
3. Most editing derives from a small set of
models.
Tunnel edits
Cross field edits
Cross record edits
Prototyping Principles
4. Most reports are based on a four step
process.
Select data from the database
Sort by specification
Format and edit for printing
Print
Prototyping Principles
5. There are a standard set of value added
design structures that should be added
Audit trails
Control totals
Menu and command
modes
Help facility
Standard screen
formats
Date/time stamping
Ergonomics
Prototyping Tactics
Normalize data to 3NF
Use component engineering
Use existing components
Assemble from existing parts
Reuse pieces
Create pieces so that they can be reused
Cut and paste
Keep a set of examples
Prototyping Tactics
Use active data dictionaries
Automate documentation
Keep teams small
Integrated software workbench tools
Specify objectives not procedures
Provide end-user report writing tools
Use professional prototypers
Have systems developers work with
prototypers
Project Management
Initial Model: 2-6 weeks
Must be fast enough to maintain interest
Revisions: immediate - 2 weeks
Chargeback: use charges to avoid frivolous
changes
Approval: determine the group who approves
iterations
Sign off: formal acceptance
Additional
Implementation
Requirements
Operational documentation and
procedures
Data size and operational impact analysis
Test plan
Training procedures
Tactic
Evolution
Throwaway
Life Cycle component
References
 Bernard H. Boar, Application Prototyping, Wiley, 1984.
 Ralph Sprague & Eric Carlson, Building Effective Decision Support Systems,
Prentice Hall, 1984.