In computing with words and perceptions (CWP), the objects of computation are words, perceptions, and propositions drawn from a natural language. The central theme of CWP is the concept of a generalised constraint. The meaning of a proposition is expressed as a generalised constraint. CWP is a necessary tool when the available information is perception-based or not precise enough to use numbers. See also Fuzzy set Lotfi Zadeh Perceptual computing Type-2 fuzzy sets and systems References L. A. Zadeh, “Fuzzy logic = computing with words,” IEEE Trans. on Fuzzy Systems, vol. 4, pp. 103-111, 1996. Soft computing