Evaluating XML-Extended OLAP Queries Based on a Physical Algebra

In today’s OLAP systems, physically integrating fast-changing data, e.g., stock quotes, into a cube is complex and time-consuming. This data is likely to be available in XML format on the WWW; thus, instead of physical integration, making XML data logically federated with OLAP systems is desirable. In this paper, we extend previous work on the logical federation of OLAP and XML data sources by presenting a 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.