1. Requirements Engineering

2. Requirements Engineering
The first step of each process model
What do we want to build?
They may range from a high-level abstract statement of a service or of a system constraint to a detailed mathematical functional specification: can be statements (“The system shall…”), diagrams, use cases, etc.
Can be used as basis for contacts, etc.

3. Requirements specify external behavior
Functional requirements are statements of the services that the system must provide
“The system shall display the heart rate of the patient”
Non-functional requirements are constraints on the services and functions offered by the system
“The system shall display the heart rate of the patient within two seconds”
Performance, Scalability, Capacity, Availability Reliability, Recoverability, Maintainability, Serviceability, Security,
Regulatory, Manageability
Exercise: list some functional and non-functional requirements for an iPhone

4. Answer: list some functional and non-functional requirements for an iPhone
The system shall make a phone call
The system shall receive a phone call
The system shall allow the user to adjust volume
etc
Non-functional:
The system shall boot up in 60 seconds or less
The system shall respond to touch within 1 second

5. Requirements qualities
Three Cs:
Clear
Consistent
Complete (internally and externally)
Use the SE principle of incrementality to derive requirements
Remember, they must all be externally visible
Why? They must all be testable

6. Exercise Give an unclear requirement, then fix it
Give an inconsistent set of requirements, then fix them
Give an incomplete requirement, then fix it*

7. Answer Unclear: “The background shall be blue”
There are many shades of blue…is #3333CC blue?
Fix: “The background shall be #0000FF”
Inconsistent: “The background shall be red” and, elsewhere “The background shall be a cool color”
Incomplete: This is the hardest; it means we’re missing a requirement or information
Fix: …make sure you have all your requirements (externally complete)
Fix: …make sure you have enough info; include supporting documents when needed (i.e. what is 508 compliance?) (internally complete)

8. Testable Requirements
Do not use vague terminology; “errors shall be minimized…”
Should NOT
partially pass
or fail
Should have
a source

9. Requirements Validation
It’s cheapest to fix faults at this step, than later on (sometimes 100 times cheaper)
Are they testable?
Do any conflict?
Do they cover all aspects of the system?
Are they what the customer wanted?

10. Quiz review What is a functional requirement?
What is a non-functional requirement?
What do all requirements have to be?

11. In-class exercises Let’s imagine we have an ATM
Come up with 5 functional requirements
Show how each requirement could be improved
Show how each requirement could have been worse
Come up with 3 non-functional requirements
Do the same as above
Complete the exercises at

12. Assignment (time permitting)
Examine the Quiz Game description
In your teams, come up with at least seven functional requirements and at least two non-functional requirements
Remember the three Cs
Requirements specify external behavior
Requirements must be testable
Turn in this assignment through svn
See instructions and grading rubric on project page