An indication of whether a value can change between two released versions of the same or .
- All released versions of the same or have the same id (field), but each version has a different effective time (field).
- If a is mutable (Mutable=YES), its value can differ from one version to the next without changing the identifier.
- If a is immutable (Mutable=NO), its value must be the same in every version of a . To change the value associated with an immutable field, the existing must be inactivated and a new must be created to replace it. The new must have a previously unused identifier. The field values are set to replace the inactivated concept with the updated information.
- The mutability for each , in each type of release file, is indicated in the release file specification table for that component type or reference set.