This code system http://hl7.org/fhir/map-model-mode defines the following codes:

CodeDisplayDefinition
sourceSource Structure DefinitionThis structure describes an instance passed to the mapping engine that is used a source of data
queriedQueried Structure DefinitionThis structure describes an instance that the mapping engine may ask for that is used a source of data
targetTarget Structure DefinitionThis structure describes an instance passed to the mapping engine that is used a target of data
producedProduced Structure DefinitionThis structure describes an instance that the mapping engine may ask to create that is used a target of data