lec 5 software complexity

What are the characteristics of good software design?

Class independence; High cohesion; Low coupling; Fault prevention and tolerance; Principle of least astonishment

What is class independence?

Classes operate with minimal reliance on other classes (high cohesion and low coupling)

What is cohesion in software?

The degree to which elements of a class belong together and serve a single purpose

What are the types of cohesion?

Functional cohesion; Sequential cohesion; Coincidental cohesion

What is functional cohesion?

All methods in a class contribute to one well-defined task (ideal case)

What is a functionally cohesive class?

A class that performs only one task and nothing else

What is sequential cohesion?

Output from one part of a class becomes input to another

What is coincidental cohesion?

Unrelated methods grouped together in a class

Why is coincidental cohesion bad?

Reduces clarity and maintainability; often leads to large class code smells

What is coupling?

The degree of interdependence between classes

What are the types/levels of coupling?

Uncoupled; Loosely coupled; Highly coupled

What is loose coupling?

Classes have minimal dependencies (ideal for flexibility)

What is tight/high coupling?

Classes have many dependencies and changes affect other classes

Why is high coupling a problem?

Changes in one class impact others, increasing complexity and maintenance difficulty

What does uncoupled mean?

No dependencies between classes

What does loosely coupled mean?

Some dependencies but manageable and preferred

What does highly coupled mean?

Many dependencies requiring refactoring

What is the Law of Demeter?

A class should only communicate with closely related classes ("only talk to friends")

Why is the Law of Demeter important?

Reduces unnecessary coupling and improves maintainability

What is the Principle of Least Astonishment?

Systems should behave in a way users expect without surprises

Why is the Principle of Least Astonishment important?

Improves usability and reduces confusion

What does KISS stand for?

Keep It Simple, Stupid

What does KISS mean in software design?

Choose the simplest solution that works

What is fault prevention?

Designing systems to avoid faults occurring

What is fault tolerance?

Designing systems to continue operating even when faults occur

What is Automatic Program Repair (APR)?

Techniques that automatically detect and fix software bugs