A digital object is not usable without a computing environment in which it can be rendered or executed. If we want to ensure the long-term usability of digital objects, so that they can be used in the face of changing formats, software, and hardware, it is necessary to either preserve their computing environments or to, at least, gather enough information, so that the computing environment can be reconstructed or adapted to a changed world. Digital preservation metadata is the information that is needed in order to preserve digital objects successfully in the long-term so that they can be deployed in some form in the future. Information that describes the sufficient components of the digital object's computing environment has to be part of its preservation metadata. Although there are semantic units for recording environment information in the de-facto standard for digital preservation metadata, PREMIS, these semantic units have rarely, if ever, been used. Prompted by increasing interest in the description of computing environments, this article describes requirements and solution proposals for defining an improved metadata description for computing environments.