Typically, a subclass augments or redefines the existing structure and behavior of its superclasses. - Grady Booch

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

is a style of enterprise application development and integration, based on using automated tools to build system independent models and transform them into efficient implementations.

Whereas object-oriented analysis typically focuses upon one specific problem at a time, domain analysis seeks to identify the classes and objects that are common to all applications within a given domain, such as missile avionics systems, compilers, or accounting software.