This paper discusses two general models of user interaction in the context of user assistance (HELP) and their implications for design. Conceptual and quantitative models provide software engineers with tools that can aid them in the interface design process. The conceptual model presented is derived using a hermeneutic approach to the analysis of human-computer interaction. The interaction is modeled as a set of states and transitions between states. This suggests that user assistance should have a more central role in the design of the system. The quantitative model is derived from a study of the existing literature, and provides a framework for analyzing performance issues at the human-computer interface, using metrics like response time, keystrokes, error rates, and task completion rates. The model contains seven components, covering user characteristics, information type, structure, user knowledge, presentation, control, and access.