Re: [ontolog-forum] What words mean

[paola.dimaio@xxxxxxxxx]

Wacek

Thanks, I think the descriptions are clear, 
I am looking for a systematic collection examples to illustrate  what is being described below - sorry I was not clear
p

>     Christopher and all
>
>     is there a rule or other guideline to prescribe when a tree should
>     have one, and when more than one root?
>

In what sense of 'should' should a tree have one or more roots?  What
sort of context (pardon) do you mean here as the source of demand for
one or more roots?

By definition (one from graph theory, Azamat might have had other
definitions in mind), a tree is a connected acyclic graph.  Undirected
trees have no roots.

A rooted tree is a directed tree with exactly one distinguished vertex
chosen as the tree's root.  Following the definition (in a rooted tree,
there is exactly one path from the root to any other vertex in the
graph), if a tree were to have two roots, each of them would have to be
accessible from the other, which implies a cycle in the graph;  but such
a graph is not a tree.

vQ

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-- 
Paola Di Maio 
School of IT
www.mfu.ac.th
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