We witness an increasing need for cross-enterprise collaboration to respond to continuous changes in market demands and opportunities. Approaches based on Web services have been proposed, mainly because they provide standards-based service abstractions which can be combined into business-oriented functions. Collaboration requirements are expressed as business processes representing the coordination of several services whose descriptions are published in service registries. Current service registries are passive and, consequently, the published service descriptions may become readily outdated. In this paper, we present an approach to guarantee the freshness and correctness of published service descriptions. Unlike existing approaches, which use a service description for each individual service, our approach uses so-called service source descriptions which specify the collection of service functionalities and contain only the information required for finding services. This description is published in the public service registry to facilitate discovery of service providers whereas the detailed information remains at the source.