Slides 23 + 24 - Examination of NL Requirements

Question 1

Formal vs. Natural Language

Answer 1

Formal specification language
 - Benefits:
   ● defined semantic
   ● fully verifiable
   ● can be automatically tested
 - Limitations / problems:
   ● known and used only by experts
   ● primarily for functional requirements

Natural language
 - Benefits:
  ● everyone uses this language
 - Limitations / problems:
  ● can be interpreted differently
  ● are incomplete, inconsistent

Question 2

NLP - Classes of Transformations

Answer 2

Deletion:
● We reduce to dimensions we are able to manage
and understand.

Generalization:
● We generalize statements and omit exceptions.
● Generalizations often go along with deletions.

Distortion:
● We formulate statements imprecisely and
ambiguously.

Question 3

Requirements Examination Process

Answer 3

1. Examine individual words of a requirement sentence!
2. Examine each requirement sentence as a whole!
3. Examine the integration of a requirement in
   the overall specification!

Question 4

Quality Costs

Answer 4

1. Defect Prevention Costs
   ● Constructive quality assurance
2. Examination and Inspection Costs
   ● Analytical quality assurance
3. Error Costs
   ● Correction
   ● Reduced revenues
   ● Compensation costs

Question 5

Pressman’s Defect Amplification Model
● Assumptions
● A phase-structured development process is applied
● We cannot to detect all defects in the phase were they were made
● A defect that is passed to the next phase leads to multiple defects

Answer 5

Assumptions:
● A phase-structured development process is applied

● We cannot to detect all defects in the phase were they were made

● A defect that is passed to the next phase leads to multiple defects

Question 6

When do we stop testing?

Answer 6

● We stop testing when the planned time is over.

● A survey among the testers revealed that they have the impression that the product could be delivered.

● Eventually stop testing, otherwise you will find still more defects.

Question 7

Test Exit Criteria

Answer 7

Relative Defect Cost
● If the average examination costs per detected defect go beyond a threshold X, the test is finished.
● The examination costs must be known!
● The threshold needs to based on experience!

Question 8

Problems of Defect Seeding

Answer 8

Problems
● Defect must be seeded homogeneously.
● Seeded defects must cover all defect types.
● Additional costs are to be expected.