As the human-computer interface becomes more pervasive and intimate, it will need to explicitly draw upon cognitive science as a basis for understanding what people are capable of doing. User experience and situation should be integrated into the computer system design process. Situational awareness can be used to reduce the amount of explicit input a person is required to give a computer. Contextual information of what and where the user task is, what the user knows, and what the system capabilities are, can greatly simplify the user scenario. Such use of contextual models in computers can also reduce the teaching needed for the user to accomplish tasks. An approach to a framework for design of contextual computing is illustrated through examples.