knowable property
Knowable is the first instant this plane could have answered with the assertion, RFC 3339: the later of Seen and the server's clock at the write. Derived and never supplied, which is what stops history filed today from being backdated into a past read.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? knowable;