Knowledge Discovery in Databases (KDD) is a complex and computationally intensive process, that requires a repeated interaction between tools and users, often in a distributed environment. Given the complexity of the process, both naïve and expert users need some support to effectively perform knowledge discovery. In this paper we present a user-and knowledge-centric approach to support the design of KDD projects. Semantic technologies are exploited to support sharing and (re-)use of KDD computational resources and processes in a distributed collaborative environment. In particular, functionalities for tool publishing, service and process discovery, and versioning of processes greatly enhance process management, and provide a learn-by-example and trial-andtest environment for collaborative KDD design. The systematic use of semantic information, a loosely-coupled and layered Service-Oriented Architecture, a cooperative and flexible approach, result in a platform natively conceived for an open, distributed and collaborative environment.