In this paper, we describe an approach to modelling context-aware 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. This information is then used to populate our context model. We describe also how the collected data can be used to validate our approach.