5.Design Principles

Designing stable boundaries so common extensions require less modification to trusted core code.

Ensuring subtypes preserve the behavioral contract expected from the base abstraction.

Keeping high-level policy independent from volatile low-level implementation details.

Grouping behavior around a coherent responsibility and a focused reason to change.

Keeping contracts focused so clients depend only on capabilities they actually use.

Reducing knowledge of distant object structure and avoiding brittle navigation through internal collaborators.

Reusing behavior through composition/delegation when subtype inheritance would create unnecessary coupling.

A practical view of SOLID and related principles for controlling coupling, responsibilities, and change.