Service Oriented Architecture (SOA) and Grid computing are very hot research topics, nowadays. While Grid computing is aimed at sharing dynamically heterogeneous resources, SOAs is a meta-architectural style that enable business flexibility in an interoperable way. There is a growing consensus that SOA(s) and Grid(s) might be beneficial to each other. In Grid-based SOAs a central role is played by tools for the publishing/discovering of services (resources). This work presents SPRanker (Service

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... Provider Ranker): a service discovery tool that is able to retrieve providers from partially specified service descriptions. It ranks providers found on the basis of an Information Retrieval-based score formula that takes into account judgments expressed collaboratively by past service users.