Without the many contributions from these dedicated and curious researchers, this publication would not exist. Thanks are also due to the many reviewers, both inside and outside of NIST, who provided helpful suggestions to improve the various ideas incorporated in this publication. We also must not ignore the significant contributions made by the designers, specification writers, and implementers who developed the proposed technologies for service discovery, which formed the basis for the analyses reported here. Without the imagination and resources of these industrial contributors, we would not be in a position to provide the knowledge we gained by studying the designs for various service discovery systems.