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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Looking for a good introduction to object oriented programming with Python
Date: Wed, 08 Aug 2012 22:59:34 -0400
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On Wed, 08 Aug 2012 20:31:57 +0100, lipska the kat
<lipskathekat@yahoo.co.uk> declaimed the following in
gmane.comp.python.general:

> A Tree consists of Node(s) and Leaf(s), relationships are modelled by 
> following the Line(s) in the Tree diagram and that is it. Line may be a 
> class as in 'the patriarchal line' I'm not sure, it would come out in 
> the iterative wash.
> 
> We can infer whatever we want from this simple model. A Leaf is a child, 
> until it becomes a parent when it becomes a Node. To anthropomorphize a 
> bit more (I love that word) and introduce non species specific words and 
> concepts, a Node can be a father or mother (simple to implement by 

	If a "node" is a father or mother, and it takes one of each to
produce a "leaf", your "tree" has just collapsed.

	In genealogy, a "tree" is merely the representation -- in one
direction -- of relationships from a single Person to either all
ancestors, or to all descendents.

	"Father", "mother", "son", "daughter" (or to simplify, "parent",
"child") are merely roles taken on by a person in relationship to
another person. A Person can exist even if we do not know who the
parents were, nor if there are any children.

> But what of all the ephemeral data that goes with a sentient existance 
> on this planet such as birth certificates, newspaper articles, 
> christenings, death certificates, photographs etc etc, what about 
> pegigree certificates, innoculation records and any other trivia, 
> information and flotsam that goes with a pedigree Dog or Horse or indeed 
> Parrot.
>
	Those documents are the /evidence/ used to prove the linkages of the
Person.

	Granted, the most popular genealogy program tends to be the least
capable -- it won't let one add a person without creating a "family"
first; and most all evidence is recorded as just a text memo.

	In contrast, TMG, provides for "Sources" (the documents),
"Citations" (references to sources, used in the events in the person's
life), "Repositories" (where the source can be found). Events cover
things like "Birth", "Marriage", "Death", "Graduation", etc. [one can
create custom events too]. Events have a date, a location, and can have
multiple citations to the source the provides evidence that the event
took place and involved the person to which it is linked. In TMG, there
is no "family" as such -- only the linkages from relationship events (a
"birth" event does not link a child to its parents; that is done via a
pair of parent-child relationships [father-relationship,
mother-relationship] and TMG supports having multiples -- only the pair
marked a "primary" is used to produce "tree-like" reports, but the
system supports having birth-parents and adoptive-parents at the same
time in the data). It even supports having multiple "Birth" events too,
if one finds conflicting evidence and can not determine if some is
invalid.

	I'm not going to go into depth, but the TMG (v8) database consists
of 29 tables, and the user interface centers on displaying a list of
events for a person. Oh, and the person can have more than one name too,
though only one can be listed as primary (shows at the top of the page)
-- the others appear as name events.

	The absolute minimum to define a person in TMG is an ID number (the
internal primary key) and preferably a "primary" name (and the name
could be all blanks -- though having multiple people with no names, just
ID numbers, makes for difficulty when later adding relationships: does
this person connect to "(---unknown---)(---unknown---)" #2718 or to
"(---unknown---)(---unknown---)" #3145 <G>)
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/