Flexible consistency modes for active databases applications

摘要

The concept of transaction is a basic one in database theory. Yet, in some cases the atomicity of a transaction may be relaxed. This happens either to avoid the damage inflicted by the fact that many data elements are locked in long transactions, or to support different view-points of the database that may relax atomicity constraints. This paper defines the concept of transaction, in the environment of PARDES—an intelligent active database and outlines a model in which different modes of consistency co-exist as local decisions. These modes are defined and analyzed. Among the basic modes are: fully consistent (consistent at all times), quasi consistent (eventually consistent) and loosely consistent (failures in derivations are not compensated). This is an extension to the active database definition language that enables the support of implementation considerations using high-level abstractions.