A view on a set of entities. It can be seen as a 'relational context', reifying a relation. For example, a PlanExecution is a context including some actions executed by agents according to certain parameters and expected tasks to be achieved from a Plan; a DiagnosedSituation is a context of observed entities that is interpreted on the basis of a Diagnosis, etc. Situation is also able to represent reified n-ary relations, where isSettingFor is the top-level relation for all binary projections of the n-ary relation. If used in a transformation pattern for n-ary relations, the designer should take care of: - creating only one situation for each instance of an n-ary relation, otherwise the 'identification constraint' (Calvanese et al., IJCAI 2001) could be violated - adding an 'exact cardinality' restriction corresponding to the arity of the n-ary relation, otherwise the designer would actually represent a polymorphic relation.