On page 13 of the SAP BusinessObjects Explorer Installation, Deployment and Administration Guide, it states
For information on sizing your system according to the usage patterns of the
users across your deployment, refer to the SAP BusinessObjects Explorer
XI 3.1 Service Pack 1 Sizing Guide available at: http://service.sap.com/bosapsupport.
A document entitled Sizing SAP BusinessObjects Explorer was posted sometime last week. You’ll need your SAP S-ID to get into the SAP Service Marketplace.