DyDa: Dynamic Data Warehouse Maintenance in a Fully Concurrent Environment

Data warehouses (DW) are an emerging technology to support high-level decision making by gathering information from several distributed information sources (ISs) into one materialized repository. In dynamic environments such as the web, DWs must be maintained in order to stay up-to-date. Recent maintenance algorithms tackle this problem of DW management under concurrent data updates (DU), whereas the EVE system is the first to handle (non-concurrent schema changes) (SC) of ISs. However, the concurrency of schema changes by different ISs as well as the concurrency of interleaved SC and DU still remain unexplored problems. In this paper, we propose a solution framework called DyDa that successfully addresses both problems. The DyDa framework detects concurrent SCs by the broken query scheme and conflicting concurrent DUs by a local timestamp scheme. The two-layered architecture of the DyDa framework separates the concerns for concurrent DU and concurrent SC handling without imposing any restrictions on the autonomy nor on the concurrent execution of the ISs. This DyDa solution is currently being implemented within the EVE data warehousing system.