I got some more information about Gemini. As Mosha said, it is Analysis Services. As you know, SSAS has always been available also as a client tool, using the same engine of the server product to create local cubes. The Kilimanjaro release will add several features to this engine that, integrated with the client part of Gemini (which allows end users to define their own model), will give high speed performance to cubes which are stored in-memory and without any pre-calculated aggregation.
According to Ashvini Sharma, these new features might not be available to traditional SSAS developers in the Kilimanjaro release. However, cubes created from end-users will expose all SSAS metadata as usual. For this reason, these cubes will be immediately available to any SSAS-enabled client.
Now, it is questionable to call these entities cubes, since (but this is my speculation) they could have a design very unusual if compared to traditional cubes.
Anyway, in the long term, all these new features (which have still not be disclosed in detail) will be available at any level. Just in the first release, the server instance of SSAS will be used by Excel Services. When you create a model into Excel, the local engine will be used. When the same spreadsheet will be published to SharePoint, the Excel Services engine will use an instance of SSAS (but may be more than one instance on more servers) to make the calculation on these data.
Unfortunately, not all information about internal details can be disclosed now. However, it seems that SSAS will have a bright future.
Originally appeared on: http://sqlblog.com/blogs/marco_russo/archive/2008/10/07/gemini-and-ssas-explained.aspx