[BioSQL-l] left_value and right_value in taxon table

[Hilmar Lapp]

Hi Eric,

On Apr 4, 2008, at 9:43 AM, Eric Gibert wrote:
> Dear all,
>
> I hope that I am not the 100th persons asking the following questions:
> 1) what are left and right values in the taxon table for?

they hold the nested set values. Nested sets are enumeration  
algorithm described in Joe Celko's SQL for Smarties books, and Aaron  
Mackey gives a good introduction here:

http://www.oreillynet.com/pub/a/network/2002/11/27/bioconf.html

(This is in the schema DDL file, though obviously should be  
documented better. Good candidate for an FAQ, I suppose.)

> 2) How are they computed

load_ncbi_taxonomy.pl recomputes them automatically after each  
update. It's a simple recursive depth-first graph traversal algorithm.

	-hilmar
-- 
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: Hilmar Lapp  -:-  Durham, NC  -:-  hlapp at gmx dot net :
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