A note on fuzzy time-series model

Recently, Song et al. [Fuzzy Sets and Systems 73 (1995) 341-348] proposed a homogeneous fuzzy time series model to model dynamic process whose observations are fuzzy sets or linguistic values by means of defining some new operations on fuzzy numbers. In this paper, we considered expanding the results to the nonhomogeneous fuzzy time series and the general fuzzy time series by using the weakest t-norm based algebraic fuzzy operations and solved the open problem suggested by Song et al. in their conclusion of the paper.