At 14:53 31/08/2010, Lukas Renggli wrote: Hi Lukas, It seems that the children keep pointing to their parent, which is the removed structure. I'd expect the children to be removed too, actually starting from the leaf nodes. So something like (not tested): PRRemoveCommand >> removeWithChildren: aStructure aStructure hasChildren ifTrue: [ aStructure enumerator contents do: [:aChild | self removeWithChildren: aChild ]]. aStructure remove PRRemoveCommand >> doExeccute [...] self removeWithChildren: self structure [...] Does this makes sense? Regards, Reza