In this paper we present MD, a logical model for OLAP systems, and show how it can be used in the design of multidimensional databases. Unlike other models for multidimensional databases, MD is independent of any speci c implementation relational or proprietary multidimensional and as such it provides a clear separation between practical and conceptual aspects. In this framework, we present a design methodology, to obtain an MD scheme from an operational database. We then show how an MD database can be implemented, describing translations into relational tables and into multidimensional arrays.