Message-ID: <4BC334E2.6020600@gmail.com>
Date: Mon, 12 Apr 2010 08:57:38 -0600
From: Rob Sargent <robjsargent@gmail.com>
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To: pgsql-sql@postgresql.org
Subject: Re: Table Design for Hierarchical Data
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	<201004080956.06446.achill@matrix.gatewaynet.com>
	<4BBDEF35.6040308@gmail.com>
	<201004121114.10189.achill@matrix.gatewaynet.com>
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Believe me: "ego-ma-pa" will correctly define genealogical relationships
(at least among humans).

On 04/12/2010 02:14 AM, Achilleas Mantzios wrote:
> Στις Thursday 08 April 2010 17:59:01 ο/η Rob Sargent έγραψε:
>> The "parent" node in a genealogy is the mother-father tuple, so given
>> that as a singularity it still fits a tree.
> No, because the child and parent node would be of different schema.
>>
>> On 04/08/2010 12:56 AM, Achilleas Mantzios wrote:
>>> Στις Wednesday 07 April 2010 23:33:07 ο/η Yeb Havinga έγραψε:
>>>> Achilleas Mantzios wrote:
>>>>> Στις Wednesday 07 April 2010 11:06:44 ο/η Yeb Havinga έγραψε:
>>>>>   
>>>>>> Achilleas Mantzios wrote:
>>>>>>     
>>>>>>> You could also consider the genealogical approach, e.g.
>>>>>>>
>>>>>>>
>>>>>>> The parents of any node to the root, i.e. the path of any node to the root are depicted as
>>>>>>> parents[0] : immediate parent
>>>>>>> parents[1] : immediate parent of the above parent
>>>>>>>   
>>>>>>>       
>>>>>> What I have more than one parent?
>>>>>>     
>>>>>
>>>>> Then it is no longer neither a tree, nor a hierarchical structure, but rather a graph.
>>>>> This a totally different problem.
>>>>>   
>>>> My question was actually an attempt to point at the inability of what 
>>>> you call the 'genealogical approach' database design to store 
>>>> information of more than one parent.
>>>
>>>
>>> Are you suggesting that we should change our definition of trees ADT, just because it does not
>>> fit the mere detail that humans have two parents?
>>> Or are you just suggesting that the "genealogical" term is inaccurate?
>>>
>>> Take a look here: www.tetilab.com/roberto/pgsql/postgres-trees.pdf
>>>
>>>>
>>>> regards,
>>>> Yeb Havinga
>>>>
>>>>
>>>
>>>
>>>
>>
> 
> 
>