This code system http://hl7.org/fhir/document-relationship-type defines the following codes:

CodeDisplayDefinition
replacesReplacesThis document logically replaces or supersedes the target document.
transformsTransformsThis document was generated by transforming the target document (e.g. format or language conversion).
signsSignsThis document is a signature of the target document.
appendsAppendsThis document adds additional information to the target document.