title: Is "node" an ADT? If so, what is its interface?
body: <p>Nodes are useful for implementing ADTs, but is "node" itself an ADT? How does one implement "node"? Wikipedia uses a plain old struct with no methods in its (brief) article on nodes. I googled node to try and find an exhaustive article on them, but mostly I found articles discussing more complex data types implemented with nodes. </p>
  
  <p>Just what is a node? Should a node have methods for linking to other nodes, or should that be left to whatever owns the nodes? Should a node even be its own standalone class? Or is it enough to include it as an inner struct or inner class? Are they too general to even have this discussion?</p>