A Methodological Framework for Data Warehouse Design 2. Analysis of the Information System 3. Requirement Specification 4. Conceptual Design

Though designing a data warehouse requires techniques completely different from those adopted for operational systems, no significant effort has been made so far to develop a complete and consistent design methodology for data warehouses. In this paper we outline a general methodological framework for data warehouse design, based on our Dimensional Fact Model (DFM). After analyzing the existing information system and collecting the user requirements, conceptual design is carried out semi-automatically starting from the operational database scheme. A workload is then characterized in terms of data volumes and expected queries, to be used as the input of the logical and physical design phases whose output is the final scheme for the data warehouse. 1. INTRODUCTION The database community is devoting increasing attention to the research themes concerning data warehouses (DWs); nevertheless, the crucial issues related to DW design have not been deeply investigated yet [14]. Designing a DW requires techniques completely different from those adopted for operational information systems. While most scientific literature on the design of DWs focuses on specific issues such as multidimensional data models [1] [8], materialization of views [2] [9] and index selection [7] [10], no significant effort has been made so far to develop a complete and consistent design methodology [12]. In [3] the different phases in DW design are described informally, but no ad hoc conceptual model to support them is devised. In this paper we outline a general methodological framework for DW design, based on the conceptual DW model we developed, called Dimensional Fact Model (DFM). The methodology we propose features 6 phases, briefly sketched in Table I and examined in Sections from 2 to 7. The issues we have already addressed are discussed in more detail; in particular, Subsection 4.1 formalizes the DFM, while Subsection 5.1 includes the definition of workload on the DFM. As to the issues we are currently investigating, an overview of the main research topics is provided. The aim of this phase is to collect the documentation concerning the pre-existing operational information system. It involves the designer, in tight collaboration with the people involved in managing the information system and, if possible, with its designers, and produces in output the (conceptual or logical) schemes of either the whole or part of the information system. Typically, this phase entails integration of heterogeneous views. This topic has been largely dealt with in the database literature, see [15] for a comprehensive …