"The notion of social worlds is used here to refer to a form of social organization which cannot be accurately delineated by spatial, territorial, formal, or membership boundaries. Rather, boundaries of social worlds must be determined by interaction and communication which transcend and cross over the more formal and traditional delineators of organization. The term social world is used here to develop a common referent for a number of related concepts which refer to similar phenomena, Thus, social world phenomena encompass that which other sociologists have referred to as: occupational contact networks, invisible colleges, behavior systems, activity systems, and subcultures. After tracing some of the sociological history of social world analysis, a series of concepts are developed which bring together and bind all of the previously mentioned concepts into a systematic whole. Major aspects of individual involvement, structural features of social worlds, levels of social world analysis, and some implications of a social world perspective are presented. In this way, a program for study and unification of related concepts is presented in preliminary form."
(David Unruh, 1980)
David Unruh (1980). "The Nature of Social Worlds" The Pacific Sociological Review, Vol. 23, No. 3 (Jul., 1980), pp. 271-296.
http://www.researchgate.net/profile/El_Sayed_El-Aswad2/publication/269110060_Social_Worlds/links/5481b1d50cf263ee1adfd991.pdf