Such properties provide the following features:
- Proxy objects can be searched by their external key property;
- Proxy objects can be linked to each other by using their external key properties and an external reference.
If a MetaProxyProperty has been configured with a Reference it is defined as an external reference. An external reference property links to a Proxy instance via its property value.
Such Proxies (its properties) will automatically reference to the instance of the targeted MetaProxy (as given by the underlying Reference) having the same entry in its external Primary Key property than the given Proxy instance.