Designing transparent interaction is important for ubiquitous computing (ubicomp). A psychology framework that characterizes user"s cognitive behavior in ubicomp environments would be invaluable for guiding the interaction design to be optimally compatible with human capabilities and limitations. By analyzing the cognitive skill and attention selectivity, such a framework is proposed in this paper. Correspondingly, a context-sensitive multimodal architecture is presented on the level of technology. A case study, where the theory was implemented in a handheld hypermedia guide and deployed into the context of authentic use, is then discussed.