We have established that a system itself can be considered as a single entity that has form and function. Now we will examine how a system decomposes into entities, each of which also has form and function. These entities are usefully represented by abstractions. The selection of the entities is guided by holistic thinking and by focus. The system is surrounded by a boundary that separates the system from its context. The following discussions examine Task 2 of System Thinking, which is stated in Box 2.4.