H7 - test

Question 1

What is a formal specification?

Answer 1

Specification based on a formal model with precise syntax & semantics.

Question 2

Why is it almost certain that you will be confronted with the “buy or build” method?

Answer 2

The presence of standards implies that a lot of people buy instead of build and therefor I will sooner or later be confronted with this.

Question 3

Explain:
Consistent, Complete, Unambiguous

Answer 3

• Consistent
  = no contradictions in the specification
• Completeness
  = all properties are defined in terms of known concepts
• Unambiguous
  = misinterpretations are impossible
  -> there is only one way to express a certain property

Question 4

What is the link of Formal Specifications with Testing and Design by Contract?

Answer 4

Testing:
to have complete coverage, we use black-box testing test-cases

Design by Contract:
The (natural) pre- and post conditions

Question 5

What types of specifications are there?

Answer 5

• Input/Output specifications
  -> include logic assertions inside algorithm
• Algebraic Specifications
  -> which operations one can apply on types
• Logic-based Specifications
  -> usage of mathematical entities
• State-based Specification
  -> behavior described in terms of state-machine

Question 6

When is an input/output specification consistent/complete/unambiguous?

Answer 6

consistent = termination
complete = correctness
unambiguous: are all parts of pre- and postcondition necessary?

Question 7

When is an algebraic specification consistent/complete/unambiguous

Answer 7

Consistent: it is never possible to deduce contradictions

complete: can all query expressions be reduced?

unambiguous: are all functions and axioms required?

Question 8

Usage of each specification:

Answer 8

Input/Output: program verification

Algebraic: specifying interfaces

Logic: specifying constraints on class models

Question 9

When is a logic-based specification consistent/complete/unambiguous?

Answer 9

Consistent: no contradictions in specification

Complete: all properties are defined in terms of known concepts

Unambiguous: misinterpretations are impossible

Question 10

When is a state-based specification complete/consistent/unambiguous?

Answer 10

Complete: every event/state pair has a transition

Consistent: every state is reachable from initial state

Unambiguous: deterministic