When trying to better understand the connection between ontologies, models, rules, and facts; I ran across this resource. It is a treasure trove of information. Specifically (this is just a sampling):
Here is a useful tidbit:
"Given the higher perspective it may be tempting to associate ontologies with meta-models, but that could be misguided because meta-models are still models whose purpose is to describe and process other models, as compared to ontologies which are only concerned with meaning and semantic consistency."
There is a lot here to be digested!