CWE

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CWE allows the end user to send a term from an arbitrary coding system in place of a term from the specified value-set in the circumstance when the concept being encoded is not represented in the specified value set, whereas CNE requires that the primary code in a message instance be from the specified value-set. Committees proposing to change the coding strength from CWE to CNE should consider whether the value set in question is sufficiently stable and comprehensive that it can support the change in coding strength. Attribute constraints expressed in a universal specification should generally be constrained only by vocabulary domains and not bound to value sets. The sole exception to the principle is the constraint “structural attributes”. (MnM motion for the Refinement Chapter, Sept2006)