Objects are the real and conceptual things we find in the world around us. An object may be hardware, software, a concept (e. g., velocity), or even "flesh and blood." Objects are complete entities, i. e., they are not "simply information" or "simply information and actions." Software objects strive to capture as completely as possible the characteristics of the "real world" objects which they represent. Finally, objects are "black boxes," i. e., their internal implementations are hidden from the outside world, and all interactions with an object take place via a well-defined interface.

p. 335; as cited in Edward V. Berard (1995) "A Comparison of Object-Oriented Development Methodologies". The Object Agency, Inc. - Essays on object-oriented software engineering (1993)