What is the best practice for validating metadata properties on a CMIS document create/update. For example, say I want to ensure that the dublincore metadata property values for nature, topic, coverage, subject, etc. belong to the list of possible values defined in their corresponding vocabularies. Would it be appropriate to extend the DublinCoreListener to perform this validation synchronously? If so, do you have examples that demonstrate the error handling and transaction rollback required in such a scenario?