Abstract. This paper describes an ontology-based approach to interaction of users and mobile robots for joint task solving. The use of ontologies allows supporting semantic interoperability between robots. The ontologies store knowledge about the tasks to be performed, knowledge about the functionality of robots and the current situation factors like a robot location or busyness. Ontologies are published in a smart space which allows indirect interaction between participants. On the basis of the knowledge, a robot can define a task that is to be performed and get the current status of other robots. The paper presents a reference model of the approach to indirect interaction between mobile robots for joint task solving, an ontology model for the knowledge organization, and application of the presented approach for the scenario for obstacle overcoming.