Conceptual database design: equivalence relations

New approaches of conceptual database design, having equivalence relations as fundamental aspects of their definitions, are introduced. Database models, model transformations, algorithms and languages are transported from databases at the boundary between concept theory and databases. A distinction is made between theory and applications. Structures for the analysis of database class/concepts, have been chosen as reference points of the class/concept space. Outside these points, other structures, can dynamically be generated. Conceptual/logical measures of quality, distinguished from numerical measures, allow to evaluate the introduced approaches. Discussions about the chosen reference points, the role of mathematics in this choice, and the value of both computer science and languages in our society are provided.