FUZZY COGNITIVE MAPS CONSIDERING TIME RELATIONSHIPS

Abstract

Causal knowledge is often cyclic and fuzzy, thus it is hard to represent in the form of trees. A fuzzy cognitive map (FCM) can represent causal knowledge as a signed directed graph with feedback. It provides an intuitive framework in which to form decision problems as perceived by decision makers and to incorporate the knowledge of experts. This paper proposes a fuzzy time cognitive map (FTCM), which is a FCM introduced to a time relationship on arrows. We first discuss the characteristics and basic assumptions of the FCM, and present a description of causal propagations in a FCM with the causalities of negative-positive-neutral interval, [-1, 1]. We develop a method of translating the FTCM, that has a different time lag, into the FTCM that has one or the same unit-time lag, which is a value-preserving translation. With the FTCM, we illustrate analysing the change of causalities among factors according to lapse of time.