ERATOSTHENES: Design and Architecture of an OLAP * System Nikos Karayannidis, Panos Vassiliadis, Aris Tsois, Timos Sellis National Technical University of Athens (NTUA) Department of Electrical and Computer Engineering Knowledge and Database Systems Laboratory Zografou 15773, Athens, Greece {nikos, pvassil, atsois, timos}@dbnet.ece.ntua.gr Abstract. On-Line Analytical Processing (OLAP) is a trend in database technology, based on the multidimensional view of data. The aim of this paper is twofold: (a) to list general problems and solutions applicable to the design of any OLAP system and (b) to present the specific design decisions that we made for a prototype under development at NTUA, which we call ERATOSTHENES. The paper addresses requirements and de- sign issues for all three models involved in an OLAP system: the presentational, logical and physical model. It also discusses in detail the architecture and the major compo- nents of ERATOSTHENES. 1. Introduction On-Line Analytical Processing (OLAP) is a trend in database technology, based on the mul- tidimensional view of data. The focus of OLAP tools is to provide multidimensional analysis to the underlying information. To achieve this goal, these tools employ multidimensional models for the storage and presentation of data. The goal of this paper is to present require- ments, design choices and architecture characteristics for OLAP systems. The perspective that we take is the one of the technology provider: we focus on the internals of an OLAP system, rather than the external behavior of the system. Moreover we present specific design choices for the architecture of an OLAP system that we develop at NTUA. ERATOSTHENES, is an internal project of the database group at NTUA and aims to pro- vide OLAP facilities to the end-user through optimized data structures and query processing techniques. The structure of this paper is as follows: in Section 2 we present the basic characteristics of an OLAP system. In Section 3 we present requirements and design problems for the con- struction of such a system. In Section 4 we give some intuition on the ERATOSTHENES system and its architecture. Finally, in Section 5 we conclude our results and provide plans for future work. * This research has been partially funded by the European Union's Information Society Technologies Programme (IST) under project EDITH (IST-1999-20722).