1. A computer program product, tangibly embodied on a non-transitory computer-readable storage medium, containing instructions to cause a data processing apparatus to: store back end system metadata corresponding to a plurality of back end systems, wherein the back end systems store service modules that execute a plurality of prebuilt queries on data stored by the back end systems, and the back end system metadata identifies the service modules stored on the respective back end systems; store service module metadata identifying the prebuilt queries that are executed by the respective service modules; store query metadata describing data types of query results generated when the prebuilt queries are executed by the respective service modules; receive, from a client, a first request, the first request identifying one of the back end systems; transmit the back end system metadata for the identified back end system to the client in response to the first request, the transmitted back end system metadata describing the service modules stored by the identified back end system; receive, from the client, a second request, the second request identifying one of the service modules stored by the identified back end system; transmit the service module metadata for the identified service module to the client in response to the second request, the transmitted service module metadata identifying at least two of the prebuilt queries executed by the identified service module; receive, from the client, a third request, the third request identifying one of the at least two prebuilt queries executed by the identified service module; and transmit the query metadata for the identified prebuilt query to the client in response to the third request, the transmitted query metadata describing data types of the query results generated when the identified prebuilt query is executed, wherein the back end system metadata, the service module metadata, and the query metadata are transmitted to the client in a normalized format, and wherein the client displays the transmitted back end system metadata, the transmitted service module data, and the transmitted query metadata.