assumptionassumption - - A statement, condition, or belief about why a logical relationship exists between entities.
Usage: Assumptions may or may not be shown or verbalized on logic diagrams, but they always exist. Further, assumptions may or may not be valid. Every logical relationship portrayed in all thinking processes (TP) logic diagrams has one or more underlying assumptions. Some assumptions are considered to be 'oxygen', that is, true and well understood by most people throughout our world, and thus, do not have to be documented. When a scrutinizer says, "what's underneath the arrow?" he or she is really asking the TP diagram creator to explain the assumption(s) that allows two entities to be logically connected.
Illustration 1: In sufficiency-based logic diagrams such as the current reality tree, future reality tree, and transition tree, an assumption is often considered to be a valid condition for the system being assessed and usually is accepted without question. The following diagram is verbalized: If 10 I have a dog then 30 I have an animal because All dogs are animals. The statement, All dogs are animals, is the underlying assumption.
Illustration 2: In necessity-based logic diagrams such as the evaporating cloud and the prerequisite tree, the rationale for the necessary condition is verbalized as follows: B In order that I have food to eat, D I must have money to buy food, because BD I must pay for food. The latter phrase is the assumption.