In this paper, we describe an approach to modelling contextaware systems starting on the knowledge level. We make use of ideas from Activity Theory to structure the general context model and to assess empirical data. We further on describe how the data-driven and the model-driven aspects of our approach are combined into a single knowledge model. We outline the design of an empirical study conducted to gather information about a concrete workplace environment to populate our context model. We further on describe how the collected data can be used to validate our approach.