This subtype of the Assessment Event is used to bind the total score concept and total score meaning properties to the proper coded values for the CAGE, and to set the limits on the total score value to range from 0 to 4. Logically, we're saying that this Assessment Event is a CAGE Assessment Event, although physically, there is little difference between this and other instrument-specific subclasses. In a database implementation, this would not result in a separate table - it would simply set the rules that dictate what the Assessment Event values may take. Not shown in this UML model is that the assessmentInstrument property must be a CAGE instrument (LOINC code TBD). This could have been done by creating an association from this class to the CAGE class using the same name (assessmentInstrument), thus redefining the parent property, but this technique can cause confusion and so the limitation on the type of assessment instrument is merely implied.