Rigorous Design of Fault-Tolerant Transactions for Replicated Database Systems using Event B

System availability is improved by the replication of data objects in a distributed database system. However, during updates, the complexity of keeping replicas identical arises due to failures of sites and race conditions among conflicting transactions. Fault tolerance and reliability are key issues to be addressed in the design and architecture of these systems. Event B is a formal technique which provides a framework for developing mathematical models of distributed systems by rigorous description of the problem, gradually introducing solutions in refinement steps, and verification of solutions by discharge of proof obligations. In this paper, we present a formal development of a distributed system using Event B that ensures atomic commitment of distributed transactions consisting of communicating transaction components at participating sites. This formal approach carries the development of the system from an initial abstract specification of transactional updates on a one copy database to a detailed design containing replicated databases in refinement. Through refinement we verify that the design of the replicated database confirms to the one copy database abstraction

Implementation of active collections framework using .NET

For many years, large distributed enterprises have faced a common problem of near real time sharing of enterprise data typically stored in databases. As these databases may be located globally, distributed nature of this data makes it difficult to access instantaneously. The Active Collections Framework (ACF) acts as a good foundation on which to build distributed applications. This framework requires distributed applications to view changes to data as events of interest. The ACF framework integrates access to data and data changes through active collections. ACF framework is based on two different research areas: event management in distributed computing and active database systems. Active databases support mechanisms to monitor changes to the database state. The central concept in ACF event management is active collections. Each active collection is a collection of all objects specified by a query on the enterprise data. For each client interested in obtaining data, an entry is made in the active collection. This information is then used by windows service to notify the registered client of any data changes. This project implements the Active Collections Framework using Microsoft .Net and Visual Studio .Net. Two sample applications using the developed framework have been developed to demonstrate the efficiency of data storage and event notification capabilities of the developed ACF framework

Improved Presentation and Facade Layer Operations for Software Engineering Projects

Nowadays, one of the most challenging situations for software developers is the presence of a mismatch between relational database systems and programming codes. In the literature, this problem is defined as "impedance mismatch". This study is to develop a framework built on innovations based on the existing Object Relational Mapping technique to solve these problems. In the study, users can perform operations for three different database systems such as MsSQL, MySql and Oracle. In addition, these operations can be done within the framework of C# and Java programming languages. In this framework, while the developers can define database tables in the interface automatically, they can create relations between tables by defining a foreign key. When the system performs these operations, it creates tables, views, and stored procedures automatically. In addition, entity classes in C# and Java for tables and views, and operation classes for stored procedures are created automatically. The summary of the transactions can be taken as pdf file by the framework. In addition, the project can automatically create Windows Communication Foundation classes to facilitate the handling of database elements created and the interfacing operations, as well. This framework, which supports distributed systems, can be downloaded at this link