Software Requirements

1
Software Requirements

• Distinguishes between Customer "needs" --
• AND
• Customer's "wants" --

2
How do we gather data to determine a Projects
Requirements?

• Observation - Watch
• Interview - Listen
• Research - Learn

3
Interview

• Determine who are the projects stakeholders!
• Talk to customers
• Talk to users
• Talk to other stakeholders

4
The Interview Process

• How many persons should attend an interview?

5
The Interview Process

• not everything spoken is the truth
• sometimes people lie or forget facts
• most often they speak from their own ignorance or
  point of view
• interview many people to gather balanced
  information
• evaluate what you are hearing
• watch body language

6
What happens after the interview?

• Immediately write down interview results.
• Research show that even in a life-and-death
  situations
• 50 of what took place is forgotten within 30
  minutes.
• Follow-up Memo

7
Observation Watch, Who, Where, Why?

• Watch the way it is done Go to the customers
  site, spend time in the users real-world
  environment!
• Who does the job?
• Where is it done?
• Why is it done in this particular way?
• Learn everything you can about the way the
  process is done. At this stage it doesnt matter
  if it is done by hand or by computer.

8
Research and Observation

• How do we get what we need?
• Obtain copies of ALL operating documents
• Assess existing documents
• Assess current procedures
• Focus on identifying whats visible
• Observe current procedures
• Cross fertilization

9
Research

• Study documentation provided by the customer.
• Collect materials generated by the existing
  system, even if such materials are
  paper-and-pencil versions
• Examine the input and output currently generated

10
Data Gathering for Software Requirements

• Analysis
• Takes practice
• Demands Prioritization
• Means Identifying Goals

11
Prioritization

• users are likely to ask for the moon if there
  are no limits.
• beauty should not outweigh functionality.
• help customer be realistic about expectations.
• useful to identify enhancements for future work
  once basic product is developed.

12
Prioritization

• Guides team in allocating effort
• May be needed to schedule incremental
  development
• Enables determination of what is really important
  
• Avoid "gold-plated" software

13
Analysis ? Specification

• The goal understanding the customer's
  requirements for a software system.
• involves technical staff working with customers
• involves all the stakeholders in the system

14
Who ARE the stakeholders?
15
What are the problems associated with the
Requirements phase?
16
Requirements gathering problems?

• Stakeholders don't really know what they want
• Stakeholders express their requirements in their
  own terms

17
Requirements gathering problems?

• Different stakeholders may have conflicting
  requirements

18
Requirements gathering problems?

• The requirements may change during the process
• New stakeholders may emerge on the scene

19
Requirements gathering problems?

• Stakeholders don't really know what they want
• Stakeholders express their requirements in their
  own terms

20
Analysis Viewpoints

• Partitioning Identifies the structural
  relationships between components
• Abstraction Identifies generalities among
  components
• Projection Identifies different ways of looking
  at a problem

21

• Social and Organizational factors effect all
  systems!

22

• Software systems are used within a social and
  organizational context.

23

• Social and organizational factors CAN dominate
  system requirements.

24
Software Viewpoints
25

• Software is not designed in a vacuum! There is
  no single correct viewpoint. Effective
  software involves combining all viewpoints.

26

• Good analysts must be very sensitive to different
  views. There is no systematic way to factor them
  into the analysis process.