From Wikipedia's definition of regular langaugesThe collection of regular languages over an alphabet $$ is defined  recursively as follows:The empty language $$ is a regular language.For each $a  $, the language $\{a\}$ is a regular language.If $A$ and $B$ are regular languages, then $A \cup B$ (union), $A  B$ (concatenation), and $A^*$ (Kleene star) are regular languages.No other languages over$ $ are regular.The regular languages also form a (full) AFL. Parallel to the concept of generator for a sigma algebra, do the regular languages form the minimal  (full) AFL (or (full) semi-AFL, full trio, trio, ...)  that contains the empty language, and  $\{a\}, a  $? In other words, are the minimal  (full) AFL (or (full) semi-AFL, full trio, trio, ...) generated by the empty language, and  $\{a\}, a  $ exactly the regular langauges? 
Generators of families of langauges?
formal languages;regular languages;closure properties