_db = parss
_table = version
_parent = parent.versions
_id = id

content
date

## Properties which are used in dynamic relations MUST be listed here, too
parent_id
parent_type

parent = object(HopObject)
parent.local.1 = parent_id
parent.foreign.1 = $id
parent.local.2 = parent_type
parent.foreign.2 = $prototype