The cast transformation function has an optional type parameter. Document that the parameter value SHOULD contain information about the target model as documented in the FHIRPath specification (http://hl7.org/fhirpath/#models), e.g.:

The cast example in http://hl7.org/fhir/mapping-tutorial.html#step4 should be updated from

"src.a21 as a -> tgt.a21 = cast(a, "integer")"

to

src.a21 as a -> tgt.a21 = cast(a, "FHIR.integer")