UMBEL (Upper Mapping and Binding Exchange Layer) has two purposes. Its first purpose is to provide a general vocabulary (the UMBEL "vocabulary") of classes and predicates for describing domain ontologies, with the specific aim of promoting interoperability with external datasets and domains. The second purpose is to provide a coherent framework of broad subjects and topics (the UMBEL "reference concepts"), suitable as binding nodes for mapping relevant Web-accessible content, also with the specific aim of promoting interoperability and to reason over a coherent reference structure and its linked resources. UMBEL presently has about 28,000 of these reference concepts drawn from the Cyc knowledge base, which are organized into more than 30 mostly disjoint SuperTypes.