Managing Query and Update Transactions under Quality Contracts in Web-Databases

Huiming Qu (Pitt/CS)

PhD Defense

Friday, August 31st, 2007
10:00am - SENSQ Eli Lilly

Abstract

In modern Web-database systems, users typically perform read-only queries, whereas all write-only data updates are performed in the background, concurrently with queries. For most of these services to be successful and their users to be kept satisfied, two criteria need to be met: user requests must be answered in a timely fashion and must return fresh data. This is relatively easy when the system is lightly loaded and both queries and updates can be executed quickly. However, this goal becomes fundamentally hard to achieve due to the high volumes of queries and updates in real systems, especially in periods of flash crowds. In this work, we argue it is beneficial to allow users to specify their preferences and let the system optimize towards satisfying user preferences, instead of simply improving the average case. We believe that this approach will empower the system to gracefully deal with a broader spectrum of workloads.

Towards user-centric web-databases, we propose a Quality Contracts framework to help users express their preferences over multiple quality specifications. Moreover, we propose a suite of algorithms to effectively perform query and update load balancing and scheduling according to user preferences. We evaluate the proposed framework and algorithms through a simulation with real traces from disk accesses and from a stock information website. Finally, to increase the applicability of Quality Contracts enhanced Web-database systems, we propose an algorithm to help users adapt to the Web-database system behavior and maximize their query success ratio.

Dissertation Adviser

Prof. Alexandros Labrinidis, Department of Computer Science

Committee Members

Prof. Panos K. Chrysanthis, Department of Computer Science
Prof. Daniel Mosse, Department of Computer Science
Dr. Ming Xiong, Bell Laboratories