1. A method of providing an application as a service in a secure environment, comprising: creating a sandbox in a user's computing environment, responsive to a request made to a computing environment that provides a marketplace for offering an application as a service: downloading the application to the user's computing environment to run within the sandbox; searching data sources associated with the user's computing environment; based on data description received with the application, establishing connectivity with data registry of the data sources; installing the application to run within the sandbox using the established connectivity, wherein the sandbox allows access to data local to the user's computing environment and prevents the data local to the user's computing environment moving to the computing environment; and automatically validating an installation of the application by discovering data specified in the data description in the data sources and determining whether the data specified in the data description exist in the data sources.