I have recently started working with semantic web and linked data technologies, I have been always confused about one thing though. What is the difference between an Ontology and a vocabulary? Which is preferable?
In the driest sense, a "vocabulary" is a context-less list of terms, with no defined interrelationships. "Ontology" is meatier, implying the presence of interrelationships, axioms, classes, etc.
Nevertheless, the term "vocabulary" is almost never used to mean ONLY "list of terms", unless it's under the umbrella of an ontology you're talking about. The two terms overlap quite a great deal, and IMO using the term "vocabulary" generally means an ontology which doesn't claim a rigidly formal philosophical backing.