From: beaurega@ireq.hydro.qc.ca (Denis Beauregard)
Newsgroups: soc.roots
Subject: Royalty and probability
Date: 8 Jan 93 16:28:11 GMT
Organization: Institut de recherche d'Hydro-Quebec, Varennes, Canada

I read a book about the roots of the Capetians, the 3rd races
of Kings of France (after Merovingians and Carolingians).

While the book (1 cm thick) gives a lot of data, it is not complete as 
there is another book (5 cm thick) about the House of Bourbon which
descendant from the Capetians.  Nonetheless, a good work.

One very interesting point is about the origin.

The concensus is that the 1st one is Robert le Fort (the Strong).
But, before him, there are some 6 or 7 hypothesis about the
previous generations.  This would give a tree like this one:

1 NAME Robert le Fort //
  2 FAMC @F123@
    3 SOUR @A456@
    3 PROB 25%
    3 NOTE The preferred hypothesis
  2 FAMC @F126@
    3 SOUR @A457@
    3 PROB 15%
  2 FAMC @F132@
    3 SOUR @A458@
    3 PROB 10%
  2 FAMC @F135@
    3 SOUR @A459@
    3 PROB 10%
  2 FAMC @F141@
    3 SOUR @A460@
    3 PROB 10%

That is:

According to source A456, he descends from family F123, but an estimate
of probability this is the right one is 25%.

According to source A457, he descends from family F126, but an estimate
of probability this is the right one is 15%.

You see the mess: we get into historical data where there are
conflictual hypothesis about parents of someone.  And this is true
in almost any tree.  That is, except for the most recent generations
when you usually know if your parents are the biological ones or if
the father is actually the father, there is always a possibility of
say 1-25% that the link is bad, and more when we take into account
of the errors in records (if marriage record gives XXX as parents and
a date and place of birth and that the corresponding birth record
gives other parents, who's right?).  The fact is that with any link
there is a probability it is the right one.

With historical data, we can weight that probability to some extent.
For example, in the above roots of Robert le Fort, there are say 7
hypothesis.  One is preferred and we can give it a probability of
25% or best.  The other have a lower probability and all can be
wrong, so we must keep some place for an 8th choice.

So, a complete genealogical tree can include probability.  In most
times, it won't, but when one is not sure about the right parents,
probability should be entered and both possibilities should appear
somehow.  I understand most software won't support this.

But, if you don't take this into account, you will face this:

You read book AAA.  It said parents of PERSON are F1 and M1.
Then, you read book BBB, which gives parents as F2 and M2.
And one more book CCC, giving parents F3 and M2 (this time, the same 
mother as another source).  Years after, you re-read book AAA.

If you don't keep track of all hypothesis, you have all persons floating
around with no relation.  When you find some new data, you have to
keep some paper or note about this in a not-structured fashion.
But, isn't it best to have it managed at the same place as the
more solid part of the tree?

-- 
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