Fuzzy multiset regular languages and their basic characterizations

The paper provides a survey of several ways how to describe fuzzy multiset regular languages, i.e., languages generated by fuzzy multiset regular grammars. These languages can also be characterized by means of fuzzy multiset finite automata (both in general and in reduced forms), fuzzy multiset regular expressions, and as fuzzy multiset languages which can be expressed in a semilinear form. Moreover, it is pointed out that a prevailing number of already published papers concerning fuzzy multiset finite automata is based on a wrong definition. It is also shown that the name ‘deterministic fuzzy multiset finite automaton’ is often used incorrectly for automata deserving adjective pseudodeterministic.