CLOS Metaobject Protocol

The CLOS (Common Lisp Object System) Metaobject Protocol (MOP) is a set of tools that allows programmers to customize and extend how object-oriented programming works within Lisp. Think of it as a way to adjust the fundamental rules and behaviors—like how classes are created, how inheritance works, or how methods are invoked—by modifying the underlying system itself. This enables developers to create new types of object behaviors or programming models tailored to specific needs, providing a high level of flexibility and control over the object system beyond standard capabilities.