1. A method for a service recommendation service [ 1001 ], comprising: determining one or more queries that do not expose additional data items stored in a data source of a participant in a collaborative information system than are exposed by queries already implemented on the participant's data source [ 1003 ]; identifying query services that are not authorized to involve the data source, but which use the determined one or more queries [ 1009 ]; and recommending the identified query services to the participant [ 1011 ].