The elements described in section 12.3.9.1 aren't really talking about immutability in the same way as we mean for 'intent'. We will remove the use of the word immutable there. While we're at it, we will provide som clearer wording in that and a related section. Will change this sentence: "In general the requisitionId, practitioner, authoredOn and subject for each will be immutable, but there may be situations where some workflows allow them to change." "In general the requisitionId, requester, authoredOn and subject for each will not change over the lifetime of the Request, particularly once the status becomes 'active', though there may be situations where some workflows allow these elements to change. Because of this, there could be situations where the subject, requester, authoredOn could differ between Requests that share the same requisitionId. Systems can enforce business rules to prevent such inconsistency from happening if it would be problematic." Will also change this sentence: "In a "replaces" relationship, the target resource is no longer in force and should have a status of "completed" or "cancelled" or some other terminal state." to add the following sentence after: "The source and target of a "replaces" relationship should have the same "intent". I.e. An order can replace another order, but can't generally replace a proposal - though an order can be "basedOn" a proposal."