Software quality improvement and cost reduction are the results expected from better communication among the people who work on a software system. SEER supports communication about a target system during the target's entire life cycle, beginning in the early stages of design, by providing access to a data base of information about the target. SEER is based on the observation that software evolution, i.e., the modification of inservice software, is becoming the dominant aspect of software engineering. SEER does not yet exist, but its functions are being defined and evaluated with the aid of a "software breadboard". An extended example of SEER use is presented, together with a description of the user's view of the SEER data base and a summary of some advanced functions possible within the SEER framework.

The designer of a computing system should adopt explicit criteria for accepting or rejecting proposed system features. Three possible criteria of this kind are input recordability, input specifiability, and asychronous reproducibility of output. These criteria imply that a user can, if he desires, either know or control all of the influences affecting the content and extent of his computer's output. To define the scope of the criteria, the notion of an abstract machine of a programming language and the notion of a virtual computer are explained. Examples of applications of the criteria concern the reading of a time-of-day clock, the assignment of capability indices, and memory reading protection in multiprogrammed systems.