Right, an ordering relation on the edge objects. facepalm That should have been obvious, but I usually think about trees in terms of vectors of children, not traditional graph theory.

I like trees too. I think that as long as computer memory is linear, our serializations are going to be linear, so even when we get holographic displays, our primary abstractions should be linearly serializable (so we don't get lost in leaky abstractions), which means trees. A graph structure built on that would have to be some form of "magic" layered on top, based on links embedded in the tree. Among other possibilities, you can make the "edges" be little independent trees that link to the "nodes".