Dionysius - a Peer-to-peer Database Management System

Abstract: With the introduction of the peer-to-peer paradigm in the world of software, a lot of applications have been created in order to such architecture. Most of them are developed for providing a data sharing service among users connected to a network and programs such as Napster, Gnutella, eMule and BitTorrent have became the so called killer-applications. However some eorts have been spent in order to develop other solutions with the usage of peer-to-peer paradigm. In the case of databases some projects are started with the general purpose of sharing data sets with other databases. Generally they push on the idea of providing the data contained in their database schemes with other peers in the network showing concepts such schema matching, mapping tables and others which are necessary to establish connections and data sending. The thesis analyzes some of such projects in order to see which of them is the most dened and well-supported by concepts and deni- tions. Hyperion Project of the University of Torono in collaboration with the University of Trento is the most promising and it aims to be one of the rst Peer-to-Peer Database Management Systems. However the common idea of considering the peer-to-peer paradigm equal to data sharing - in the way presented by applications such as Napster or others - leads to a lot diculties, it is hard to handle the data sets, some operations must be done manually and there can be some cases where the peer-to-peer paradigm is not applied at all. For this reason the goal is to dene and show the concept of peer-to-peer database built from the scratch with a suitable DBMS for it. A real denition of peer-to-peer database has not been ever made and here for the rst time we tried to give one according to our vision. The denition depends on some precise concepts such global schema - which is the original design of the database -, sub-schema - a well logical dened sub-set of entities of the original schema - and binding tables - necessary to allow the creation of constraints and relations among the entities. Then to show the validity of such concepts and how a management system for peer-to-peer databases can be developed and used, a prototype (named Dionysius) has been realized by modifying HSQLDB - an ordinary DBMS developed in Java - and adding the peer-to-peer platform by using the JXTA libray set.