We are developing an “action science” approach to human-computer interaction 1992, seeking to better integrate activities directed at understanding with those directed at design. The approach leverages development practices of current HCI with methods and concepts to support a shift toward using broad and explicit design rationale to reify where we are in a design process, why we are there, and to guide reasoning about where we might go from there. We represent a designed artifact as the set of user scenarios supported by that artifact and more finely by causal schemas detailing the underlying psychological rationale. These schemas, called claims, unpack wherefores and whys of the scenarios. In this paper, we stand back from several empirical projects to clarify our commitments and practices. © 1992, ACM. All rights reserved.