In this report we introduce user modelling for planning lifelong learning. In Section 3 we clarify some issues relating to personalisation for lifelong learning and propose an architecture for user models interoperability. After some fundamental introductory notes about user models ontology engineering methodologies in Section 4, the development of the proposed ontology is demonstrated in details in Section 5. In Section 6 we list the possible ways of using our ontology, named Lifelong Learner Ontology (LLO). Finally, we finish with a use case scenario for user models interoperability in section 7.