Description
In today’s OLAP systems, physically integrating fast-changing data (e.g., stock quotes) into a cube is complex and time-consuming. The data is likely to be available in XML format on the World Wide Web (WWW); thus, instead of physical integration, making XML data logically federated with OLAP systems is desirable. In this article, we extend previous work on the logical federation of OLAP and XML data sources by presenting simplified query semantics, a physical query algebra, and a robust OLAP-XML query engine, as well as the query evaluation techniques. Performance experiments with a prototypical implementation suggest that the performance for OLAP-XML federations is comparable to queries on physically integrated data.