  The type of algebraic structures which form such a characteristic class \(\bK\) for some system \(\bS\) of MVL usually may come from two different sources. A first source may be determined by extralogical considerations which distinguish some such class of algebraic structures. If a system \(\bS\) of MVL is, however, determined syntactically or by a single characteristic matrix, such a class of algebraic structures often is determined by the (syntactical or semantical) Lindenbaum algebra of \(\bS\), and in such a case often plays also a crucial role within an algebraic completeness proof. The algebraic structures in \(\bK\) have a similar role for \(\bS\) as the Boolean algebras do for classical logic.