Re: Hierarchical Relationship

Bernard Peek <Bernard_at_shrdlu.com> wrote:

>In article <38bf0301.7784057_at_news.shuswap.net>, Gene Wirchenko
><genew_at_shuswap.net> writes
>
>>Bernard Peek <Bernard_at_shrdlu.com> wrote:
>>
>>>In article <89liln$7h0$1_at_news1.xs4all.nl>, John Smith
>>><someone_at_microsoft.com> writes
>>>>Hi,
>>>>
>>>>I am trying to make a Familytree in Access.
>>>>In simplified form I have made
>>>>2 tables: TblPerson and TblParents
>>>>and 1 Querie: QryPerson&Parents.
>>>>
>>>>In TblPerson I have the basic properties of a person (ID, Name, sexe etc.).
>>>>In TblParents I have 3 fields: Person_ID, Father_ID and Mother_ID
>>>>
>>>>TblParents is linked 1-to-1 with TblPerson by [TblPerson].[ID] and
>>>>[TblParents].[Person_ID].
>>>>The other 2 fields (Father_ID and Mother_ID) are fields that look up their
>>>>values in TblPerson.
>>>>
>>>>QryPerson&Parents joins the 2 tables so that I get 1 recordset of a person
>>>>including who his parents are.
>>>>
>>>>So far so good but there is one problem. I'd like to build in some
>>>>validation. For example; one should not be able to select a distant
>>>>offspring or a distant ancestor as a parent.
>>>
>>>You can probably do enough validation by looking at the date of
>>>birth/death and making sure that nobody marries someone born more than a
>>>hundred years earlier.
>>
>> That latter is not an absolute constraint.
>
>True. It's probably better for the front-end system to query data rather
>than rejecting it.
>
>>
>>>Other validation rules could get a little tricky, I do know someone
>>>whose family tree has a loop in it. It wasn't legal but it happened
>>>anyway.
>>
>> How could a loop be possible? I think you mean something else:
>>what?
>
>Someone married their granddaughter.

     That's about what I thought you meant, but it isn't a loop. It does complicate the family tree though when different generations marry. If the husband and wife are, say, two and three generations descended from a common ancestor, imagine how their kids will be related to their cousins. There would be two different ways of figuring it.

Sincerely,

Gene Wirchenko

Computerese Irregular Verb Conjugation:

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     You have biases.
     He/She has prejudices.