_db = parss
_table = topic
_parent = root.psh.topics
_id = id

url
updated
created
modified

metadata = mountpoint(Metadata)
metadata_source = metadata

_children = collection(Subscription)
_children.local = id
_children.foreign = topic_id
_children.accessName = subscriber_id

#versions = collection(Version)
#versions.local.1 = $id
#versions.foreign.1 = parent_id
#versions.local.2 = $prototype
#versions.foreign.2 = parent_type