separates a System from its Environment or from its sub and supra systems
The distinction system/environment is the Starting Point for Luhmann’s systems theory. No system is independent of its environment, since a system is constituted drawing a boundary through its operations and thereby differentiating itself from what does not belong to it, i.e., its environment.
Information crossing a boundary between a system and its environment or between a system and its sub or suprasystem must do so by means of a Transducer which leads the information across the boundary from the language of the system to the language of the environment. Confusion sometimes arises in complex systems when an activity overlaps different system and sub-system boundaries.
In many systems, Perspectives or conditions may be different depending on how close they are to that system's boundary. In the natural environment, there are many examples of specialized boundary areas which are systems in and of themselves of which the shore line the tree line are perhaps the most familiar.
In all three cases (novice outside the skill, person outside the organization, outside judgment), a procedure provides a ground for dialogue over a boundary ... books 
A similar situation applies in an organization where staff members who spend most of their time representing the organization in its external environment will have a very different view from those whose activities are primarily internal. Sales and procurement staff, researchers, planners, and lobbyists have different perspectives from one another and from that held by the front office staff. # SOURCE the word boundary refers to a setting of limits originally it applied primarily to territorial boundaries.
# EXAMPLES • a fence • the skin of the human body • a national border • the end of a retail season • the limits of a class in set theory # NON-EXAMPLES • a particular decision track in an anasotomic reticulum, which is like trying to trace the origin of a particular bucket of water back through a river delta • a link in a chain of causality • any limit to a human ability when the available technology is not specified such as "a day's journey"
# PROBABLE ERROR • misidentifying or mixing system and subsystem boundaries • failure to take into account the different boundaries assumed by different observers of a system • the assumption of the relevance of some technology which may well be superseded # SEE System; Information; Complementarity; Environment; Transducer