A contraindication is just a negation of a reason, i.e. it gives a condition under which the action is not to be done. Both, source and target can be any kind of service; target service is in criterion mood. How the strength of a contraindication is expressed (e.g., relative, absolute) is left as an open issue. The priorityNumber attribute could be used.
\nhttp://terminology.hl7.org/CodeSystem/v3-ActRelationshipType
where concept is-a CIND