The authors present a generalization of a paper by Schoett [1] for algebras containing carrier sets that are not term-generated. Reading this lengthy paper is tedious because the authors introduce many nonclassical notions. They do not justify their choices. It is not clear to me why the problem could not have been solved by using the classical technique of extending the signature by constants, using one constant for each carrier that is not term-generated.
The paper fails to mention the seminal work of Bidoit and Hennicker on the implementation of abstract data types, which supersedes a large number of classical results [2].
The paper is of purely theoretical interest. In view of its deficiencies, it can only be recommended to those who are specifically interested in a generalization of Schoett’s results.
