Design Principles

Question 1

bad software design exhibits at least one of which 3 traits?

Answer 1

Rigidity, Fragility or Immobility (While still satisfying main requirements)

Question 2

Define: Rigidity

Answer 2

Rigid if software is hard to change, because every change effects many other parts of the system

Question 3

Define: fragility

Answer 3

System is fragile if, when changes are made, unexpected parts of the system break

Question 4

Define: Immobility

Answer 4

Immobile if system is hard to use in another app, because it is difficult to disentangle from current app

Question 5

Define: System

Answer 5

A set of cohesive modules working together to satisfy a set of requirements

Question 6

Define: Pre-Condition

Answer 6

Checking the validity of an input before it is used

Question 7

Define: Post-Condition

Answer 7

Condition that must evaluate to true after the execution of some code

Question 8

Define: Coupling

Answer 8

How reliant a module is on its neighbors

Question 9

Define: Cohesion

Answer 9

The strength of a relationship between a module and its neighbors

Question 10

Define: System Boundary

Answer 10

The definition of what aspects are part of the system, and which aspects are not.

Question 11

Define: Single Responsibility Principle

Answer 11

every module or class should have responsibility over a single part of the functionality provided by the software, and that responsibility should be entirely encapsulated by the class

Question 12

Rule for connections between modules

Answer 12

If a system has n modules, the # of connections should be closer to (n-1) than to (n(n-1)/2)

Question 13

Layers vs. Partitions

Answer 13

Layers: Reliant on other layers to function Increases coupling
Partitions: Not reliant on other partitions to function. Decreases coupling

Question 14

Perks of high cohesion?

Answer 14

Complexity is manageable

Good code readability and reusability

Question 15

Features of Modularity

Answer 15

De/Recomposability
Understandability
Continuity
Protection

Question 16

Define: Modular Continuity

Answer 16

System satisfies continuity if a small change to the specification triggers a change in only one/few modules

Question 17

Define: Modular Protection

Answer 17

System satisfies protection if, when an abnormal condition occurs at runtime, the effect of such will either stay confined to that module or to few neighboring modules

Question 18

Define: Modular Understandability

Answer 18

System satisfies modular understandability if its modules can be understood independently/mostly independently

Question 19

Define: Modular Reusability

Answer 19

Components should be sufficiently independent from their source of existence

Question 20

Why are modules w/ high coupling undesirable?

Answer 20

A change in one module usually forces a ripple effect of changes in other modules.
Assembly of modules might require more effort and/or time due to the increased inter-module dependency.
A particular module might be harder to reuse and/or test because dependent modules must be included.

Question 21

Countermeasures in a class with low cohesion?

Answer 21

Try to group like functionalities into another class

Question 22

Pro/Cons of Manager Objects?

Answer 22

Pros:
Related functionalities are grouped.
Easier to manage components from single location.
Cons:
Violates the ‘single responsibility principle’, class is less robust as a result

Question 23

Define: Modular Decomposability

Answer 23

If construction method helps to break up a large software problem into smaller less complex sub-problems, we consider it to be modularly decomposable