Abstract. In this paper we present MD, a logical model for OLAP systems, and show h o w it can be used in the design of multidimensional databases. Unlike other models for multidimensional databases, MD is independent o f a n y speci c implementation (relational or proprietary multidimensional) and as such i t p r o vides 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 t h e n s h o w h o w a n MD database can be implemented, describing translations into relational tables and into multidimensional arrays.

We discuss a proposal for the implementation of the model management operator ModelGen, which translates schemas from one model to another, for example from object-oriented to SQL or from SQL to XML Schema Descriptions. The operator can be used to generate database wrappers (e.g., object-oriented or XML to relational), default user interfaces (e.g., relational to forms), or default database schemas from other representations. The approach translates schemas from a model to another, within a predefined, but large and extensible, set of models: given a source schema S expressed in a source model, and a target model TM, it generates a schema S expressed in TM that is "equivalent" to S. A wide family of models is handled by using a metamodel in which models can be succinctly and precisely described. The approach expresses the translation as Datalog rules and exposes the source and target of the translation in a generic relational dictionary. This makes the translation transparent, easy to customize and model-independent. The proposal includes automatic generation of translations as composition of basic steps.

Abstract. We describe the development of a tool, called MDM, for the management of multiple models and the translation of database schemes. This tool can be at the basis of an integrated CASE environment, supporting the analysis and design of information systems, that allows different representations for the same data schemes. We first present a graphtheoretic framework that allows us to formally investigate desirable properties of schema translations. The formalism is based on a classification of the constructs Used in the known data model into a limited set of types. Then, on the basis of formal results, we develop general methodologies for deriving "good" translations between schemes and, more in general, between models. Finally, we define the architecture and the functionalities of a first prototype that implements the various features of the approach.

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