I intended to model user preferences using ontology but I just come across Mind Mapping which look to me a little bit similar. Please what are there differences?
As I understand it, the meaning of the relationships between nodes in a mind-map are unspecified. In formal ontologies, this meaning between relationships between nodes is much more strictly controlled. But ontology is a broad term that can be understood in a philosophical or a more computer-science oriented way. I think that you could probably say that in its philosophical interpretation, a mind-map can be seen as a type of ontology.