[Zope-dev] RFC: RelationAware class for relations between objects

[Roché Compaan]

* Shane Hathaway <shane@zope.com> [2003-05-02 18:47]:
> Well, perhaps I am incorrect in my thinking, but every discussion I can 
> Google (heh, I finally used Google as a verb) that mentions both the 
> entity-relationship model and the relational model explains it 
> differently.  First they introduce ERM then explain how to implement it 
> using relations in a relational database.  ERM seems to be described as 
> the underlying model for relations.
> 
> There are a few places that mix the use of relation and relationship. 
> In some contexts, the two words are synonyms, and it seems like some 
> authors use both words loosely.  I'd be happy to be proven wrong (so I 
> can agree with you.)  Is there a model that defines "relationship" as 
> the concrete form of "relation", as you explained it?  It seems to be 
> the other way around. :-)

I don't think there is a model that defines relationship as I've
explained it, I was merely thinking of the definition of the words
"relation" and "relationship". I am happy to stick with "relationship"
if "relation" is confused with its use in existing theory.

> >Iow, Relationship should subclass ComputedAttribute? I tried something
> >like that but ran into some problems and just wanted to get something
> >out there for comment.
> 
> Ok.

As a matter of interest how will get a handle on the instance if you
subclass ComputedAttribute and don't initialise it with a function of
the class where the Relationship is created?


-- 
Roché Compaan
Upfront Systems                 http://www.upfrontsystems.co.za