In daily human interactions spatial reasoning occupies an important place. With this ability we can build relations between objects and people, and we can predict the capabilities and the knowledge of the people around us. An interactive robot is also expected to have these abilities in order to establish an efficient and natural interaction. In this paper we present a situation assessment reasoner, based on spatial reasoning and perspective taking, which generates on-line relations between objects and agents in the environment. Being fully integrated to a complete architecture, this reasoner sends the generated symbolic knowledge to a fact data base which is built on the basis on an ontology and which is accessible to the entire system. This work is also part of a broader effort to develop a complete decisional framework for human-robot interactive task achievement.