NiagaraCQ is a scalable continuous query system designed to handle a large number of queries in Internet databases. It addresses the challenge of supporting millions of queries by grouping similar continuous queries based on their structures, which allows for shared computation, reduced I/O costs, and efficient handling of timer-based and change-based queries. The system employs incremental group optimization, query-split schemes, and dynamic re-grouping to maintain performance and scalability. Experimental results demonstrate the effectiveness of these techniques in improving query execution times and reducing resource usage. The paper also discusses the implementation details and related work, highlighting the system's architecture and key components.NiagaraCQ is a scalable continuous query system designed to handle a large number of queries in Internet databases. It addresses the challenge of supporting millions of queries by grouping similar continuous queries based on their structures, which allows for shared computation, reduced I/O costs, and efficient handling of timer-based and change-based queries. The system employs incremental group optimization, query-split schemes, and dynamic re-grouping to maintain performance and scalability. Experimental results demonstrate the effectiveness of these techniques in improving query execution times and reducing resource usage. The paper also discusses the implementation details and related work, highlighting the system's architecture and key components.