anchor.diff:          let airshipSystem = ecs.RegisterSystem (SystemJunctioned<Airship, World> ())
   
           // define our airship system's update behavior
  -        let subId = ecs.Subscribe EcsEvents.Update (fun _ _ _ world ->
  +        let subscriptionId = ecs.Subscribe EcsEvents.Update (fun _ _ _ world ->
               for i = 0 to airshipSystem.Components.Length - 1 do
                   let comp = &airshipSystem.Components.[i]
                   comp.Transform.Value.Enabled <- i % 2 = 0
  
positive.code:                   Transform = ecs.Junction systems.[0] entityId
                    Skin = ecs.Junction systems.[1] entityId }
              member this.Disjunction systems entityId ecs =
                  do ecs.Disjunction<Transform> systems.[0] entityId
                  do ecs.Disjunction<Skin> systems.[1] entityId
                  
  
      let example (world : World) =
  
  
negative.code: open Nu
  module EcsTests =
  
      type [<NoEquality; NoComparison; Struct>] Skin =
          { mutable RefCount : int
            mutable Color : Vector4 }
          interface Component with
  