[Zope3-dev] Yet Another Relations (aka Reference) Engine...

[Reinoud van Leeuwen]

On Fri, Nov 11, 2005 at 03:50:25PM +0100, Helmut Merz wrote:
> 
> A relation is an object providing the IRelation interface. This 
> has got two attributes ('first', 'second' - dyadic relation) or 

I've done this kind of thing in relational databases. Problem with 'first' 
and 'second' is that it seems to imply some order. And if I try to find 
all relations from an object I allways have to compare my ID to either 
first or second.

I solved my problem by chopping a relation into three parts: the relation 
itself and both endpoints. In my database this generated an extra table 
(and some more work when writing queries), but the solution became more 
generic and flexible in the end.

(See the database diagram on 
http://www.drbob.org/datamodel/drbob_datamodel.htm . The two endpoints of 
a relation are stored in two object_link records, the relation itself in 
one link record.) 

-- 
__________________________________________________
"Nothing is as subjective as reality"
Reinoud van Leeuwen    reinoud.v at n.leeuwen.net
http://www.xs4all.nl/~reinoud
__________________________________________________