A semantic mapper is tool or service that aids in the transformation of data elements from one namespace into another namespace. A semantic mapper is an essential component of a semantic broker and one tool that is enabled by the Semantic Web technologies.
Essentially the problems arising in semantic mapping are the same as in data mapping for data integration purposes, with the difference that here the semantic relationships are made explicit through the use of semantic nets or ontologies which play the role of data dictionaries in data mapping.