Time-Phased Schedule and Level of Effort provide a milestone chart identifying each separate human factors activity to be undertaken, and show the anticipated start date and duration of each activity. As Chapanis points out, the HEPP is NOT intended to provide solutions. It is a program of activities to study a customer's problem and to try and find an acceptable solution to that problem. So, it is more like a plan of action, or a framework within which human engineering activities will be carried out. We are talking here about documents, and in many cases for complex systems, lots of them.
Engineers often have to produce a tremendous amount of paperwork in the development of a system.
The documents are represented by rows in this figure. For instance, a draft of the operational concept document is completed during the operational need determination phase of the project, while the final version of that report is delivered in the concept exploration phase. A specification is a detailed and precise presentation of the technical and operational requirements for an entity. It does not, however, contain implementation detail. A build-to specification gives that detail.