We consider the view maintenance problem in a web-based environment, in which clients query information from databases, stored in the form of materialized data warehouses, without accessing the original data sources. In addition to base data, data w arehousesalso contain highly aggregated and summarized information suitable for decision support. As changes are made to the data sources, the warehouse views must be updated to re ect a consistent state of the data sources. Recomputation is often too expensive. We describe in this paper an incremental view maintenance method basedon the net c hanges on base table, to maintain the views e ciently in the presence of aggregation and summary information. An architecture of a web-based data w arehousing system is described to minimize the workload of the data warehouse. Finally, w e develop a prototype application utilizing the new maintenance algorithm and conduct a performance study based on the prototype, comparing it with existing maintena...