In this paper we focus on a contextual domain ontology representation aiding in the process of knowledge-assisted multimedia analysis. Previous work on the detection of high-level concepts within multimedia documents is extended by introducing a "mid-level" ontology as a means of exploiting the visual context of images, in terms of high-level concepts and mid-level region types they consist of. More specifically, we introduce a context ontology, define its components, its relations and integrate it in our knowledge modelling approach. In previous works we have developed algorithms to address computationally efficient handling of visual context and extraction of mid-level characteristics and now we expect these diverse algorithms and methodologies to be combined in order to exploit the proposed knowledge model. The ultimate goal remains that of efficient semantic multimedia analysis. Finally, a use case scenario derived from the beach domain is also presented, in order to demonstrate a possible application of the proposed knowledge representation.