Re: dual graph
Date: Mon, 26 Jun 2006 19:31:05 GMT
> Chris Smith wrote: >
>>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
>>Well, such a graph has no cycles, so it is a forest. If it's connected,
>>then it's a tree.
> > I would have thought that to call an acyclic graph a tree, it would > have to have a distinguished node. Yes? No? My answer to > David's question would have been "acyclic." But again: not my field.
A DAG is acyclic and not every DAG is a tree. Is a DAG acyclic only in the sense that the edges are directed? And would not be acyclic if the edges were undirected? I think that makes sense to me. Received on Mon Jun 26 2006 - 21:31:05 CEST