On Sun, October 17, 2010 21:41, John F. Sowa said:
> On 10/17/2010 6:21 PM, Rich Cooper wrote:
>> But wouldn’t that hierarchy [of professors & grad students]
>> be a lattice instead of a tree? (01)
It seems to me that the graph would have many disconnected subgraphs,
and certainly not be a single tree. (02)
> That depends on what relation between prof & students you intend
> to represent. The relation (X took a course from Y) could have
> cycles. But the relation (X earned a PhD with Y as thesis advisor)
> would be a tree, except in rather unusual circumstances. (03)
Consider people who have multiple PhDs in different subjects.
They almost certainly have different thesis advisiors for the
different PhDs. Such not so common, but not unusual, circumstances
would make the graph no longer a forest. (04)
The unusual case would be when there was a loop. This could happen if
a professor were to go for another PhD after a number of years, and
have as a thesis advisor in the new field a former student or even
student of a student. (05)
-- doug foxvog (06)
> John (07)
=============================================================
doug foxvog doug@xxxxxxxxxx http://ProgressiveAustin.org (08)
"I speak as an American to the leaders of my own nation. The great
initiative in this war is ours. The initiative to stop it must be ours."
- Dr. Martin Luther King Jr.
============================================================= (09)
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