The main steps in the authoring process
Expressions are produced as part of a process including the appropriate knowledge and resources. As part of this process occasionally expressions will fail validation (step 4), following which a review involving the check list ( step 3) is required. The commonest problem is a simple "syntax" error, or it may be that invalid (new or inactive) SNOMED terms are used in the expression which are not in the validation server version which currently lags behind by over a year. If new terms are used these will need to be validated separately.
The final step in the process (step 5) should be a review and clinical sign off, considering that it is quite possible to construct and validate an expression which does not make sense. Step 3 above (Transform and Classify) refers to the terminology server design 5.2.5 Validate and Transform Expression, which describes the system processes.