• Parnas' Law¹⁾

• Object-Oriented Design

• Use the lowest possible visibility for a variable or method
  • Make all attributes private and use getter and setter methods to access them
  • Better also avoid getters and setters
  • Find suitable abstractions for data types and use appropriate methods instead of just getters and setters
• Avoid aliasing problems with value objects
  • If the programming language supports that use call-by-value objects (like stack objects in C++, structs in C#, records in Delphi, etc.) for value objects like Date, Money, EMailAddress, TelephoneNumber, etc.
  • Otherwise use immutable objects which are handled call-by-reference but needn't be copied
• Avoid aliasing problems with lists and similar data structures
  • Copy internal list objects before returning them or only return a read-only interface to them

See section contrary principles.

David Parnas: On the Criteria To Be Used in Decomposing Systems into Modules

• Keep It Simple Stupid (KISS): Not adhering to IH/E is often easier.

• Model Principle (MP): IH/E demands having an interface for a module which hides the inner workings. MP tells how such an interface can look like.
• Liskov Substitution Principle (LSP): For subclasses you can waken encapsulation by having a wider protected interface which can be used by subclasses. For these cases LSP has to be considered, too.
• Tell, don't Ask/Information Expert (TdA/IE): Encapsulation is about not having getter methods returning constituent internal parts of a module. TdA can be another reason for that.
• Low Coupling (LC): Higher forms of couplings (especially content couplings) break encapsulation.
• Principle of Separate Understandability (PSU): IH/E is about constructing a module in a way that hides the inner workings so it can be used without knowing them. PSU on the other hand is about constructing a module such that its inner workings (and its usage also) can be understood without knowledge about other modules.
• Easy to Use and Hard to Misuse (EUHM): A module should be properly encapsulated in order to make it easy to use and hard to misuse.

Stub

• EncapsulationDefinition
• Encapsulation (object-oriented programming)

• InformationHiding
• Information hiding

• Java World: Encapsulation is not information hiding
• EncapsulationIsNotInformationHiding

• OnDecomposingSystems