Lecture 5: High Level Requirements Specification

1
Lecture 5 High Level Requirements Specification

• Anita S. Malik
• anitamalik_at_umt.edu.pk
• Adapted from Schach (2004) Chapter 10

2
Requirements Phase

• Process of discovering the clients requirements
• Misconception
• Must determine what client wants
• I know you believe you understood what you think
  I said, but I am not sure you realize that what
  you heard is not what I meant!
• Must determine clients needs
• Familiarity with application domain

3
Requirements Analysis Techniques

• Interviewing (primary technique)
• Structured interviews
• unstructured interviews
• Questionnaires
• Forms analysis
• Video cameras
• Use Cases/Scenarios
• Rapid prototyping

4
Interviews

• Structured Interviews Specific pre-planned close
  ended questions are posed e.g., How many.,
  How often., How fast.
• Unstructured Interviews Open-ended questions are
  asked e.g., What do you think about.
• Interviewer prepares a written report outlining
  the results of the interview

5
Scenarios

• Scenarios are another widely used technique for
  requirements elicitation
• Includes expected sequence of events as well as
  all exceptions
• List actions comprising the scenario, a
  storyboard, series of diagrams depicting the
  sequence of events etc. are some techniques used
  for depicting scenarios
• Starting state, expected sequence of events,
  finishing state and exceptions to the expected
  sequence
• Use Cases are widely used form of scenarios pre
  conditions, normal flow, post conditions
  (Discussed in detail in Object-Oriented Analysis)

6
Rapid Prototype

• Hastily built (rapid)
• Key functionality
• What the client sees
• Experimentation and change

7
Human Factors

• Client and intended users must interact with the
  user interface
• Human-computer interface (HCI)
• Menu, not command line
• Point and click
• Windows, icons, pull-down menus
• Human factors must be taken into account
• Lengthy sequence of menus
• Expertise level of interface
• Uniformity of appearance
• Advanced psychology vs. common sense?
• Rapid prototype of HCI obligatory

8
Rapid Prototype as Specification Technique

• No specification phase
• Rapid prototype replaces specification document

9
Rapid Prototyping as Specification Technique

• Specifications Rapid prototype plus list of
  additional features
• Advantages
• Speed
• No ambiguities, omissions, contradictions
• Disadvantages
• Specification document is contract
• Testing requires specifications
• Maintenance requires specifications
• Conclusion Do not use rapid prototype as
  specifications

10
Testing Requirements

• Aim establish clients real needs
• Users should be given the opportunity to review
  requirements document or experiment with rapid
  prototype (if there is one) so that their
  feedback and suggestions can be implemented in
  the final product after approval from the client
  (Note Client may not be the user of the product)
• Issues must reach client
• Requirements should be numbered for requirements
  traceability

11
Metrics for the Requirements Phase

• Measure of requirements volatility how
  frequently the requirements change during the
  requirements phase and after the requirements
  phase
• How often is a screen used or not used when
  clients and users experiment with the prototype
  system

12
Challenges of the Requirements Phase

• Employees of the client organization feel
  threatened by computerization
• Requirements team members must be able to
  negotiate
• The clients needs may have to be scaled down
• Key employees of the client organization may not
  have the time for essential in-depth discussions
• Flexibility and objectivity are essential

13
Air Gourmet Case Study

• Ref (Schach 2004) pages 308 through 311
• Airlines provide special dietary requirements
  food to their passengers
• Advantages and disadvantages
• What does Air Gourmet do?
• What modifications does Air Gourmet want in its
  system?
• The text suggests building a prototype. How would
  the interview technique work?