Interface Segregation Principle "Customers should not rely on methods they don't use." Robert C. Martin
Open-closed Principle "Software entities (classes, modules, methods, etc.) should be open for extension, but closed for modification" Bertrand Meyer
Liskov Substitution Principle "Subclasses must be able to replace base classes without the client code noticing." Barbara Liskov
Single Responsibility Principle "A module (e.g. a class) should have one, and only one, reason to change." Robert C. Martin
Role-Based Access Control How to restrict access based on user roles within an organization? NIST (National Institute of Standards and Technology)
Proxy How to control access to an object through a representative or surrogate? The Gang of Four (GoF)
Singleton How to ensure that only one (or a limited number) of instances of a class can exist? The Gang of Four (GoF)