Traits of a container based on its mapping semantics.
| Type | Definition | Description | 
| has_data | True only if the container is not a "set" type. | Data indicator. | 
| has_compound_data | True only if the container is not a "set" type or "map" type. | Compound-data indicator. | 
| mapping_level | The number of mapping-levels the container supports (1 for "set" types or "map" types). | Mapping-level indicator. |