AbstractÐThis paper examines and proposes an approach to writing software specifications, based on research in systems theory, cognitive psychology, and human-machine interaction. The goal is to provide specifications that support human problem solving and the tasks that humans must perform in software development and evolution. A type of specification, called intent specifications, is constructed upon this underlying foundation. Index TermsÐRequirements, requirements specification, safety-critical software, software evolution, human-centered specifications, means-ends hierarchy, cognitive engineering.

A haemodynamic monitoring and control task was used to evaluate the ecological approach to interface design for complex high-technology environments. Guidelines proposed by Bennett and Flach (1992) were used to design multilevel displays that made visible (a) anatomical constraints, and (b) causal constraints on haemodynamic systems. These displays were compared with a traditional display that showed pressure and ¯ ow values in ® ve separate graphs. Simulations of clinical problems were generated by a computer model and presented in an interactive computer environment. Critical care nurses and nursing students observed changes in pressures and ¯ ow corresponding to certain disease states and corrected those states using simulated drugs. For both groups, speed and accuracy were progressively improved by the enhanced, multilevel displays. 1.

Traditional power system displays are limited in their ability to allow power system operators to rapidly assess faults in a power grid. New visualization techniques for displaying power systems data have been developed to aid operator performance for detecting and diagnosing faults in a process control simulation. The integrated one-line diagram (part mimic display and close spatial proximity display) and a color contour enhancement were implemented as visualization techniques in this experiment. Participants were required to detect and acknowledge a power grid system failure and diagnose contingencies that would occur in the form of voltage value fluctuations. The voltage value had to be below a threshold limit to be considered a violation. Participants were then required to identify and acknowledge all voltage violations and then go on to correct and solve the violations by switching in capacitors that are electrically closest until all violations are solved. Twenty-eight participants were randomly assigned to a tabular and separate static map board display condition (tabular), an integrated oneline diagram display condition (one-line), or an integrated one-line with color contours display condition (contour). The proximity compatibility principle predicted that the one-line and contour display would better support the divided attention task of integrating information for solving, while visual search models predicted that the tabular display would better support the focused attention task of detecting. Results generally supported these predictions. Implications for the design of power system displays are discussed. 1 1.