Requirements Prototyping

1
Requirements Prototyping

• Prototyping is used in both requirements phase
  and the design phase to
• demonstrate a concept
• demonstrate options
• interface
• technology
• etc.
• demonstrate feasibility to reduce risks
• In Requirements phase prototyping may be used
  for
• requirements elicitation especially in the UI
  area
• requirements validation performance or
  functional completeness and consistency

2
Prototyping Process

• Establish the Prototyping Objectives
• do not try to do too much and escalate cost and
  time
• consider some non-obvious usage of prototype
• early training
• early test plan
• early documentation
• initial version for iterative development
• Define Prototype Functionality
• Develop the Prototype
• Evaluate the Prototype
• Document the results from the Prototype

3
Two Major Prototyping Approaches

• Prototype thats kept (Evolutionary)
• no clear or formal requirements specification
• system is built and modified in piecemeal form
  and kept
• the final delivery is the solution system itself
• Prototype that is a Throw Away
• detailed requirements specification is written as
  the prototyping results come in, analyzed, and
  validated
• the final delivery is the requirements
  specification
• Evolutionary is very popular when there is new
  technology, especially with UI. (e.g. Web
  applications)

4
Evolutionary Prototyping
Build Prototype
Try out the Prototype
Minimal Specification
Is the Prototype adequate ?
NO
Note that there may not be any Final
Specification but there is a lot of user
interaction to perform usage verification
and validation.
YES
Deliver the Solution
5
Pros and Cons of Evolutionary Prototyping

• Advantages
• delivery speed (when everything goes well because
  the skipping of the formal specifications and
  reviews are removed)
• heavy user involvement throughout the development
  of the solution (increments of prototype are
  utilized -or tested- as soon as they are
  implemented)
• Disadvantages
• Not suited for large, complex projects where
  documentation is needed, more formal reviews are
  needed, and tighter management control is needed
  (when something goes wrong, there are not enough
  information for management to deal with).
• Continual modifications and changes, which may be
  unspecified, in the prototype make maintenance by
  others (even original authors) extremely
  difficult
• High possibility of scope creep which can cause
  increase in cost and time, forcing most of the
  work performed be charged under time and
  material basis. (This makes fixed bid a
  dangerous route.)

6
Move Towards Incremental Development Process
Define Major Requirements
Develop a High Level Design
Specify an Increment
Develop an Increment
NO
Increment Adequate ?
Use the Increment
Integrate Increments
Yes
No
System Increment Adequate ?
Use the Increment as Part of System
The key here is that there is an
architecture or high level design to
provide a general structure.
Yes
Deliver the Solution
7
Throw-Away Prototyping
Develop Prototype
Evaluate Prototype
Requirements Specification
Requirements Outline
If more clarification needed
Feeds into Design
8
Throw-Away Prototype

• Main purpose is to clarify requirements
• Advantages
• provides an early check, clarification, and
  validation of requirements
• provide an early assessment of risks
• non-code form (e.g. UI) may be quick and cheap
• Disadvantages
• the prototype many not have many reusable code
• may be pressured to keep and deliver the
  prototype code (e.g. technology prototype may not
  be user friendly or the code written is not
  easily maintainable))

9
Tools for Rapid Prototyping

• Visual Program Development
• Visual Java, Visual Basic, Visual C which
  allows
• screen display UI and
• processing function prototyping
• Special Functional and Logic Lisp and Prolog
• Database Centered Application Development
• Progress and Forte class of 4GL development
  environment
• some relational database
• reports, query, etc. processing
• Database vendor development environment
• Oracle application development (e.g. Oracle
  Forms, Oracle 9i)
• Web Based Application Development
• Active Server Page, Java Server Page, WebSphere,
  etc.

10
Reusing Components in Prototypes

• Integrating a complete application into the
  prototype
• a spreadsheet or a word processor application
• a database such as Access or SQL
• a complete legacy application
• Integrating individual components within some
  standard framework
• JavaBeans or MS DCOMs (e.g. read mail, save text,
  etc.)
• CORBA based application components