As stated, properties are represented in the index using RDF predicates, which are URIs. For example, an alternative title property for a product or artifact might use the URI http://purl.org/dc/terms/alternative. When creating a property, you might name it using a URI. If you do not supply a URI, but enter just a simple name, the system generates a URI for you. This generated URI is local to the current server. If you supply a URI, you can enter the full URI, or you can use a prefixed name, such as dcterms:alternative, where the prefix is a known abbreviation for all but the last part of the URI.
The list of prefixes is configurable. The following list discloses the default set: