A model of independence and overlap for transactions on database schemata
ADBIS'10 Proceedings of the 14th east European conference on Advances in databases and information systems
A Simple Model of Negotiation for Cooperative Updates on Database Schema Components
Proceedings of the 2011 conference on Information Modelling and Knowledge Bases XXII
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Supported by the Comissao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) and Universidade Federal da Paraiba, Brazil.In this paper we present a new cooperative transaction model. The model has been developed using a data-driven approach, where we have not considered constraints specific to one application class, but only data-specific constraints. This approach is more general than the application-driven approach adopted in other cooperative transaction models. The notion of set of complementary objects is intrinsic here. Two objects belong to a set of complementary objects if they are connected by dependency relations, directly or transitively. A set of users, represented by cooperative transactions, shares the consistency preservation of a set of complementary objects (global consistency). Responsibilities are separated: the set of complementary objects is divided into disjointed subsets, each being manipulated by at most one user. Global consistency is achieved by selective cooperation between users in order to take into account the dependency relations between the respective objects that they manipulate. The model enforces two grades of selective cooperation. In weak cooperation, a user makes his final effects visible to another (one-way cooperation). In strong cooperation users make their intermediate effects symmetrically visible (two-way cooperation). A weak or strong cooperative unit is the execution of a set of transactions cooperating weakly or strongly. A cooperative unit is hierarchically structured to reflect the hierarchical structure of the complex object associated with it. Correctness criteria define the required conditions where a cooperative unit can be terminated while ensuring global consistency. Global consistency is ensured when there are concurrent transactions external to the cooperative unit, and in case of failure.