anchor.diff:  
           // track registration
           if registered then
  -            changes.Add struct (entityId, true)
  +            changes.Add (HierarchyAdd (nodeId, entityId))
   
           // register correlation
           if registered && not isolated then
  
positive.code: 
          // track registration
          if unregistered then
              changes.Add struct (entityId, false)
  
          // unregister correlation
          if unregistered && not isolated then
  
negative.code:         ListTree.findAll (fun system -> system.Name = nodeIdStr) |>
          Seq.iter (fun system ->
              system.GetEntitiesCorrelated () |>
              Seq.map (fun correlated -> changes.Add (HierarchyRemove (nodeId, correlated)); correlated) |>
              Seq.iter (fun correlated -> system.UnregisterCorrelated correlated |> ignore<bool>))
          systemDict.Remove nodeId
  
  