Re: Co-optation Today

On Tue, 08 Jan 2008 19:51:20 -0800, John Harshman
<jharshman.diespamdie@xxxxxxxxxxx> wrote:
Here: a nested hierarchy is a set of groups in which each group has one
of two relationships with each other group; either the two groups are
wholly disjunct, or one group is entirely included within the other.
Partially overlapping groups are right out. Phylogenies can further be
described as natural nested hierarchies: only one hierarchical
arrangement of groups will work.

Actually a nested hierarchy is simply a directed rooted tree
structure, that is, an connected graph without cycles where each node
has no more than one parent (edge directed toward the node) and has
zero or more children (edge leaving the node). Such trees are
commonplace in programming.

.

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