Actually, they don’t… Typical situation: Agent A uses ontologies 1, 13, 15 A connects to Agent B, which uses ontologies 13, 52, and 57 With no other support, A might well ignore information in vocabularies 52 and 57, even though the domains of ontologies 15 and 52 overlap But if a merged ontology 15/52 exists, A can use it to make deductions involving facts from 52.