Now something which actually was proposed as a model of memory. Taken from Cognition by Posner, pp 86-89 (PSY BH:P 084), and Computational Semantics edited by Charniak and Wilks, pp 198-200 (PSY KH:C 038). Both these show a diagram of the hierarchy. Note that further experiments showed the model to be invalid.
From the point of view of the design stance, we see that a rational designer would try optimising storage (storage space is always limited). One way to do so is to store the properties as few times as possible. So instead of tagging each bird with the property ``has wings'', we just add the property once, to the topmost appropriate node.