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 specific 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.