University of Twente Student Theses


Detecting synchronization conflicts for horizontally decentralized relational databases

Gerritsen, Jan-Henk (2012) Detecting synchronization conflicts for horizontally decentralized relational databases.

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Abstract:A horizontally decentralized relational database consists of multiple separate databases that have the same database schema. These separate databases are referred to as local databases. In a horizontally decentralized database the structure of the data is the same at all local databases, only the actual data can be different. The goal of this master thesis was to develop a solution which identifies synchronization conflicts when synchronizing two local databases of a horizontally decentralized relational database. These synchronization conflicts are identified by comparing the operations executed at the local databases and not by comparing the database states. Two local databases are in a synchronized state if the database states of these two local databases are equal and do not violate any of the integrity constraints defined in the database schema. This master thesis investigated in which ways different combinations of operations could lead to synchronization conflicts based on unequal database states or violations of integrity constraints defined in the database schema. The results of this investigation were formalized in a set of theorems that can be used to identify synchronization conflicts for sequences of operations executed at two local databases. A conflict detection solution was implemented based on the conflict detection theorems. This conflict detection solution was validated against a set of test scenarios executed at a test environment of the Dation Dashboard application. Dation Dashboard is an information system for driving schools developed by the company Dation. This validation identified some problems with the approach that should be investigated further in future research. One of the problems identified for the conflict detection solution in its current form are that there are some database schema practices that can lead to the detection of a lot of unnecessary conflicts. Another problem that was identified is that a single action of a user can lead to multiple database operations, and for some of these operations the conflict detection solution can detect conflicts while no conflict is expected from the user’s point of view. The principal conclusion of this master thesis is that the conflict detection solution proposed in this master thesis seems promising, but there are several problems that should be addressed before it can be used in a production environment.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:54 computer science
Programme:Computer Science MSc (60300)
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