Re: dual graph

David Cressey <dcressey_at_verizon.net> wrote:
> Thanks to everybody for clearing up the matter of "planar".
>
> Now, I'm interested in a a subset of the planar graphs.
>
> It's the graphs that don't divide the space into more than one region.
>
> It seems to me that it's appropriate to call such graphs "hierarchical
> graphs", or simply "hierarchies". But I'm not sure. Can anyone clear this
> up?

Well, such a graph has no cycles, so it is a forest. If it's connected, then it's a tree. I don't know where Dmitry got "ordered". Any graph (planar or not, cycles or not, doesn't matter) may be made into an ordered graph simply by defining an order for its nodes.

-- 
Chris Smith - Lead Software Developer / Technical Trainer
MindIQ Corporation