1. At least one application program interface (API) embodied as one or more computer executable instructions stored on a computer-readable medium, which when executed by at least one processing system in conjunction with at least one application program that issues at least one call on a host-environment object on behalf of content, enables the content to interact with a selected hosting environment, the at least one API comprising: at least one interaction interface in the content for indicating at least one desired interaction with any one of a plurality of hosting environments; and at least one interaction expression in the at least one interaction interface for identifying the at least one desired interaction to the at least one application program without providing implementation instructions associated with the any one of the plurality of hosting environments.