Operators and Comparisons of Hesitant Fuzzy Linguistic Term Sets

The theory of hesitant fuzzy linguistic term sets (HFLTSs) is very useful in objectively dealing with situations in which people are hesitant in providing linguistic assessments. The purpose of this paper is to develop comparison methods and study the aggregation theory for HFLTSs. We first define operations on HFLTSs and give possibility degree formulas for comparing HFLTSs. We then define two aggregation operators for HFLTSs: a hesitant fuzzy LWA operator and a hesitant fuzzy LOWA operator. In actual application, we use these operators and the comparison methods to deal with multicriteria decision-making problems with different situations in which importance weights of criteria or experts are known or unknown.