Out of the Tar Pit

Question 1

The system must retain input data when ___

Answer 1

there is a possibility that the system may be require to refer to it in the future.

Question 2

Input data corresponds to ___ state.

Answer 2

essential

Question 3

In the ideal world, control ___.

Answer 3

can be completely omitted

Question 4

In the ideal world, concurrency is ___ state.

Answer 4

accidental

Question 5

In the ideal world, concurrency is considered accidental because ___.

Answer 5

finite computations take zero time, regardless of parallel or sequential ordering

Question 6

Two cases to consider regarding input data:

Answer 6

1. There exists a possibility the system may be required to refer to the data in the future.
2. There is no such possibility.

Question 7

In the ideal world, control is ___ state.

Answer 7

accidental

Question 8

In the ideal world, ___ should not appear in the formal requirements.

Answer 8

control

Question 9

Control should not appear in the ideal world’s formal requirements because ___.

Answer 9

they are derived with no consideration of execution

Question 10

It is recommended to avoid ___ in a system.

Answer 10

Accidental Useless Complexity (state / control)

Question 11

It is recommended to separate ___, ___, and ___ in a system.

Answer 11

Essential Logic
Essential Complexity (state)
Accidental Useful Complexity (state / control)

Question 12

Definition: Referential Transparency

Answer 12

When supplied with a given set of arguments, a function will always return exactly the same result.

Question 13

In the ideal world, all state in the system is visible to the user because ___.

Answer 13

inputs can reasonably be expected to be visible in ways that internal cached state is not

Question 14

Referential transparency guarantees elimination of one weakness of testing: ___

Answer 14

a system that is in one state reveals nothing about its behaviour in a different state

Question 15

Because the ideal world removes all non-essential state, ___.

Answer 15

all the state in the system is visible to the user

Question 16

Derived data is either ___ or ___.

Answer 16

immutable

mutable

Question 17

Immutable derived data

Answer 17

Data that is intended only for display

Question 18

Mutable derived data

Answer 18

Explicit requirements specify that users must be able to update the data

Question 19

All data mentioned in users’ informal requirements is ___.

Answer 19

essential

Question 20

Essential data specified in informal requirements do not necessarily correspond to ___.

Answer 20

essential state

Question 21

“Have you tried rebooting?” is advice that attempts to solve errors by ___.

Answer 21

returning the system to a ‘known’ / ‘good’ state (probably)

Question 22

If a stateless procedure uses any stateful procedures, even indirectly, then it ___.

Answer 22

can only be understood in the context of state

Question 23

You will only ever discover that you did not ___ when the system breaks.

Answer 23

write the correct tests with the correct inputs

Question 24

Complexity is primarily contributed to by (3)

Answer 24

state
flow of control
volume of code

Question 25

Object-Oriented Programming mitigates complexity by ___.

Answer 25

coupling state and behaviour

Question 26

Functional Programming mitigates complexity by ___.

Answer 26

avoiding state & side-effects entirely (in its pure form)

Question 27

Normal approach to testing is:

Answer 27

1. begin with a clean / initial / known state
2. run desired tests with test inputs
3. assume system will perform the same way every time the tests run with those inputs

Question 28

The flaw in the normal approach to testing is that ___.

Answer 28

it ignores hidden internal state

Question 29

The same problem (that testing in one state reveals nothing about the system in another state) also applies to ___.

Answer 29

test inputs

Question 30

Testing shows ___, but not ___.

Answer 30

bugs

a lack of bugs

Question 31

The more powerful a language is (e.g. manual memory management, permitting state), the harder it is to ___.

Answer 31

understand systems constructed in it

Question 32

Encapsulation allows the programmer to control and enforce ___ by ___.

Answer 32

integrity constraints over an object’s state

regulating access to that state through its methods

Question 33

Code volume should be ___.

Answer 33

reduced to an absolute minimum

Question 34

Most systems’ complexity exhibit a nonlinear increase with ___.

Answer 34

the amount of code

Question 35

Objects consist of: (2)

Answer 35

state

a set of procedures for accessing and manipulating that state

Question 36

Extensional identity

Answer 36

items are considered the same if their attributes are the same

Question 37

Essential complexity

Answer 37

Complexity that is inherent in, and the essence of, the problem (as seen by the users)

Question 38

Input data that may be required to refer to in the future corresponds to ___ state.

Answer 38

essential

Question 39

Immutable Essential Derived Data (3 qualities)

Answer 39

1. can always be re-derived from input data / essential state whenever required
2. no need to store it in ideal world
3. corresponds to accidental state

Question 40

Ideal World has 3 steps:

Answer 40

1. Gather informal requirements
2. Formalize these requirements
3. Execute the formal requirements on the underlying general purpose infrastructure