In our previous work we have introduced a novel social media that performs collaborative filtering on situations. This enhances user situation awareness with a collaborative effort to learn about importance of situations. In this paper we focus on defining a conceptual graph-based model used to represent situations in our system, so that it would (1) be consistent with existing formal definitions of situation, and (2) enable logical manipulations on situations, namely their detection and semantic generalization, which we employ in the system. In particular, we show how the latter can be accomplished thanks to situation lattices, which we adapt for the model.