XMLA overview

ThinOLAP Home has a few short articles on using XMLA, a vendor independent way of using web services to query OLAP and data ming models instead of vendor-specific APIs. It is supported by Microsoft, Hyperion, SAS, and a few smaller vendors right now. Oracle is a hold out on adopting the standard, going for the JOLAP specification instead.

Here's a SAS presentation with a pretty easy to read overview of XMLA. And Mark Rittman has a great summary on XMLA vs JOLAP.