What is an ontology? | Ontogenesis

I just read an excellent blog posting on the definition of an ontology: What is an ontology? | Ontogenesis. The only complaint I have is that the authors don't say anything about the difference between the real world and information about the real world or the difference between open world and closed world. This allows some database or OO designers to think they are building ontologies. For example, a job applicant might be the role a person plays with respect to a particular job. In the HR department, they treat the database record about the applicant as the applicant himself. In addition, every person has exactly one biological mother, but a database about people may not record that relation, so its multiplicity might be optional or even disallowed. Thus, databases and OO systems should subset and possibly augment an ontology to lend semantics to their elements, but they are rarely ontologies.