A NOTE ON A FUZZY TIME SERIES MODEL OF FUZZY NUMBER OBSERVATIONS

Song et al.[3] proposed a new fuzzy time series model by means of defining some new operations on fuzzy numbers. They presented the new model in the form of two theorems, which indicate that the value of F(t) at t+1 can be related to its previous ones by means of forward and backward linguistic difference, as a necessary condition for the homogeneous fuzzy time series. In this note, we prove that it is also a sufficient condition for the homogeneous fuzzy time series.