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Elliotte Harold wrote:
> Hunsberger, Peter wrote:
>> I don't get the distinction. As soon as you've got a graph you've got a
>> tree (or perhaps many trees).
> Not necessarily. All trees are graphs but not all graphs are trees.
> For instance a pure tree can't represent a cycle but a graph can.
> XML's rule that a node can only have one parent is not a limit of
> graphs in general.
I think he meant a spanning tree, i.e. one that has all the nodes but
all edges. A graph can have many spanning trees.
This works for undirected edges. For directed, there might not be a
spanning tree in the mathematical sense, but you can still
get one if you reverse the arrows, like in this one
o -> o <- o