JOLAP, or Java's attempt at an open way to query OLAP

OLAP - JOLAP has one developer's experience with JOLAP, which is all too familiar. Mondrian is an open source OLAP engine (the only one I know about), and is about the only engine popularaly known for supporting the JOLAP spec (although there are several commercial engines that do, including Oracle and Hyperion, among others). However, even though it is what will pop up in most search engines, it doesn't really support JOLAP yet, grudgingly leaning toward MDX and XMLA.

Mark Rittman in the pas has written up some good analysis on JOLAP and XMLA.

JPivot is the preferred (and open source) front end for Mondrian, and it too supports MDX fairly well.

I wish there were more open source alternatives for OLAP front ends (not to mention back ends). It seems to me an engine to create ROLAP friendly output is attainable by a grassroots effort with available tools, but no one has decided to bite that off yet.