Optimizing Monitoring Queries over Distributed Data

Scientific data in the life sciences is distributed over various independent multi-format databases and is constantly expanding. We discuss a scenario where a life science research lab monitors over time the results of queries to remote databases beyond their control. Queries are registered at a local system and get executed on a daily basis in batch mode. The goal of the paper is to study evaluation strategies minimizing the total number of accesses to databases when evaluating all queries in use an abstraction based on the relational model with fan-out constraints and conjunctive queries. We show that the above problem remains np-hard in two restricted settings: queries of bounded depth and the scenario with a fixed schema. We further show that both restrictions taken together results in a tractable problem. As the constant for the latter algorithm is too high to be feasible in practice, we present four heuristic methods that are experimentally compared on randomly generated and biol...

• Type: Conference
• Year: 2006
• Where: EDBT
• Authors: Frank Neven, Dieter Van de Craen
• Keywords: Conjunctive Queries, Database, EDBT 2006, Independent Multi-format Databases, Super Sequence Problem