PIW Relationships Modelling

Marco Stahl marco.stahl at gmx.net
Sun Jul 17 16:04:08 EDT 2005


> Von: Chad Knepp <pyg at galatea.org>
>  > Something like 
>  > 
>  > entity     |  output
>  > ----------------------
>  > Leguminosae  nitrogen
>  > animal       shit
>  > 
>  > would simplefy the adding of new plants(and other entitys), creating
>  > patterns for groups of plants(and other entitys), adding/changing 
>  > properties/patterns for whole plant(entity)groups.
> 
> My proposal attempts to solve this with the use of sets.  Example:
> 
> entity              |  output
> --------------------------------------
> set(all Leguminosae)   nitrogen fixing


Maybe I'm wrong, but I thought in MySQL:
"A SET datatype can hold any number of strings from a PREDEFINED list of
strings specified during table creation."

That doesn't sounds like "easy updating" or adding user contributed
rules,plants :-)

> Ok, I'm still not sure about why this is important but I see it at
> best as being 5-6 levels of hierarchy which will not affect
> performance.  Something like: 
> 
>   entity | parent
>   ---------------
>   creature NULL
>   animal   creature
>   plant    creature
>   leguminosae plant
>   soya     leguminosae
>   max	   soya
>   'Chiffumy' max
> 
> The real problem with this is that entity will not be unique which
> requires you to know a little more about the entity than just the top
> level.

Sorry i don't understand, "not unique"???
In my example tables I use the names just because of readability.
Every entity should have a unique numeric ID ('Chiffumy'=143423425).

Saludos, Marco

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