Read First: Object Type, Mapping The domain of a mapping is the set of things which may be given to the mapping as input. For example, the domain of the mapping from people to their names is the type Person. A mapping may return nothing, that is, the empty set, for some members of the domain (see hasImage/isImageoOf. It is an error to give the mapping something that is not in its domain. See the summary with example at Place Relation. Read First: Object Type, Mapping