Data that isn't part of core persistent or core data, but used for State or Reporting purposes
to avoid complex or expensive derivation (transient in nature).
It maybe accompanied as part or with the main Entity. Also, the main entity may support multiple
types of
AuxData so its unlikely it will publicly acknowledge its association with this type of data;
any relation must be kept instance specific rather than any public interface level.
Since the data is transient, depending on the nature this data isn't always reliable and
should be avoided in mission critical
application logic or part of interface definitions.
If Aux data is itself persisted for reporting; that isn't counted as part of actual entity persistence.