Increasingly, professional communicators design and evaluate information systems (ISes) (e.g., online help, websites, databases). Yet the dominant theoretical frameworks (computational psychology, formalism) and research methodologies for designing and evaluating ISes are limited in important ways. These Cartesian frameworks tend not to explore rhetorical issues: society, culture, history, interpretation. I address these issues with a theory and a research methodology (a theory-guided research approach) that I developed by conducting five empirical studies of IS use;I critique existing theories and research methodologies, then draw on scholars such as Mikhail Bakhtin, Lev Vygotsky, Yrjo Engestrom, Edwin Hutchins, and Charles Bazerman to develop a theory of artifacts adapted from genre theory and activity theory. My theory posits five tenets: activities are cyclical and developing; artifacts are interpreted segments of the material environment; artifacts' rules are complex, relatively stable, co-developing, and socially distributed; artifacts instantiate cultural-historical traditions; and artifacts occupy ecologies;I develop the theory and research methodology through qualitatively and quantitatively analyzed empirical studies of how software developers write and interpret programs (i.e., program production and comprehension); how personnel in city engineering, law enforcement, and traffic safety interpret and use a database; and how workers and college students interpret and use a geographic information system;The studies suggest that any IS is part of a cluster of co-developing genres that collectively mediate activities. In such genre ecologies , off-screen genres are often imported into the interface, mingling with on-screen genres to produce genre hybrids;These studies also suggest that a given IS's usability, though customarily conceived as a quality of the IS itself, is distributed across the entire genre ecology and the activities it mediates. I use a tripartite structure to investigate usability: contradictions in the activity engender discoordinations among genres, manifesting as interpretive breakdowns;Through these studies, I refine the research methodology that involves tracing breakdowns users encounter when using an IS, then analyzing those breakdowns to diagnose and address deeper design issues. The methodology can help designers to (a) design ISes that support users' activities; (b) recognize and design for users' genre ecologies; and (c) design the very activities that the artifacts mediate.