Building data integration systems today is largely done by hand, in a very labor-intensive and error-prone process. In this paper we describe a conceptually new solution to this problem: thatof mass collaboration. The basic idea is to think about a data integration system as having a finite set of parameters whose values must be set. To build such a system the system administrators construct and deploy a system "shell", then ask the users to help the system "automatically converge" to the...