We consider the problem of mapping data in peer-to-peer systems. Such systems rely on simple value searches to locate data of interest. However, different peers may use different values to identify or describe the same data. To accommodate this, peer-to-peer systems often rely on mapping tables that list pairs of corresponding values for search domains that are used in different peers. We illustrate how such tables are used in the Genomics community by expert curators. We then argue why mapping tables are appropriate for data mapping in a peer-to-peer environment and motivate the problem of managing these tables. The work presented here is part of the Hyperion Project [4].