UPDATE TRANSLATION IN INSTANCE MAPPED HETEROGENEOUS PEER DATABASES

摘要

In data sharing systems, peers are acquainted through pair-wise data sharing settings/ mappings for sharing and exchanging data. Besides query processing, supporting update exchange for interchanging data between peers is one of the challenging problems in data sharing systems. In update exchange, an update action posed to a peer is applied to the peer’s local database instance and then the update is propagated to the related peers. Previous work on update exchange have considered update propagation considering schema-level mappings between peers, which are conceptually similar to the view maintenance problem. However, there are data sharing systems, where peers are acquainted by instance-level mappings. In such a system, peers use different schemas and data vocabularies to represent semantically same real world entities. The instance-level mappings express how data in one peer relate to data in another peer. One of the problems in exchanging updates in instance-mapped data sharing systems is to translate updates correctly between heterogeneous peers. The translation should be such that insertions, deletions, and modifications of the tuples made by an update in a peer and by the translated version of the update in an acquainted peer are related through the mappings between them. In this paper, we investigate such a mechanism for translating update actions between heterogeneous peer data sources. Before discussing the translation mechanism, the paper first formalize the notion of update translation and derive conditions under which the translation mechanism will produce correct translations of updates.