1	import Base
2	import ./world.bend as W
3	import ./relation_types.bend as T
4	
5	# Descriptor selection belongs to the declaration, not to a queued request.
6	type Operation<S:Data> is Data:
7	  Relate{source:W.Handle<S>,target:W.Handle<S>}
8	  Unrelate{source:W.Handle<S>}
9	  Reorder{parent:W.Handle<S>,children:List<&2,W.Handle<S>>}
10	type Reason is Data:
11	  RelationError{error:T.Error}
12	  HierarchyRequired{}
13	type Outcome<S:Data> is Data:
14	  Applied{graph:T.Graph<S>,operation:Operation<S>}
15	  Refused{graph:T.Graph<S>,operation:Operation<S>,reason:Reason}