If an abstraction is a kind of some other abstraction, or if it is exactly equal to the sum of its components, then inheritance is a better approach - Grady Booch

As a noun, design is the named (although sometimes unnamable) structure or behavior of a system whose presence resolves or contributes to the resolution of a force or forces on that system. A design thus represents one point in a potential decision space. A design may be singular (representing a leaf decision) or it may be collective (representing a set of other decisions).

#The availability of high-quality Model Compilers and Virtual Execution Environments (VEEs) that provide "out of the box" platforms upon which Executable UML models can execute. These VEEs, which exist today in a somewhat incipient stage, will someday soon reduce low-level system architectures to near-commodity status.

An operation is some action one object performs upon another in order to elicit a reaction.