On varieties of rational languages and variable length codes. II
[Part I, cf. the second author, ibid. 23, 169-196 (1982; Zbl 0481.20042).] The first main result states that if \({\mathcal V}\) is a *-variety of languages closed under product, then it is described by its finite prefix codes: this means that there is a class \({\mathcal C}\) of codes such that \({\mathcal V}\) is the smallest variety containing all \(C^*\), for C in \({\mathcal C}\). The second main result describes the languages of the *- variety corresponding to the variety of monoids V*W, where the *-variety associated to W is closed under concatenation of languages, and where V*W denotes the variety of monoids generated by the semi-direct products of monoids in V by monoids in W.
scientific article; zbMATH DE number 3964196
scientific article