The language must be backwardly compatible with any version of the language that has previously been adopted as an IHTSDO SNOMED International standard. This means that any expression that is valid based on the previous SNOMED CT Compositional Grammar standard
Based on correct parsing using the ABNF specification
should also be valid based on this updated version. Please note that this requirement does not preclude extensions to the language which do not affect its backward compatibility.
Requirement G.2: Consistency