[ZODB-Dev] Re: [Zope3-dev] PROPOSAL: ZODB Relationships

[sean.upton at uniontrib.com]

This is not the case in digital media management applications where, for
example, you have a large repository of assets that need to be composited
into a whole (well, multiple wholes - that's the problem).  You could make
the argument that the container should be the whole, but this is inflexible.
Cardinality/direction to relationships is important for content management
applications becuase there is a big difference between "Has Part" and "Is
Part Of" (DCMES qualifier language), or other sorts of relations.  Also the
source/derivative asset relationship has direction.  In media composition
(media assets composing a product visually or organizationally), hierarchies
are a virtue of that particular product, but in media companies, we are very
big on the idea of re-using content in other products, which may have
different hierarchies using the same assets.

Sean

-----Original Message-----
From: Roché Compaan [mailto:roche at upfrontsystems.co.za]
Sent: Friday, May 09, 2003 4:01 AM
To: Chris Withers
Cc: pje at telecommunity.com; zodb-dev at zope.org
Subject: Re: [ZODB-Dev] Re: [Zope3-dev] PROPOSAL: ZODB Relationships


On Fri, 09 May 2003 10:38:51 +0100
Chris Withers <chrisw at nipltd.com> wrote:

> Roché Compaan wrote:
> > What we have at the moment is a graph and strictly speaking a graph has
> > no direction in its edges (maybe you meant directed graph). As far as I
> > can see graphs are possible, hierarchies are not. Can't one just use
> > containment to represent hierarchies? If one can what other use cases
> > are there for directionality in associations?
> 
> You can only use containment once ;-)
> 
> I can't think of any good examples, but if you wanted to express more
> than one relationship that wasn't direction-agnostic, then you
> couldn't use containment for both of them.
> 

Maybe I wasn't too clear. If you want to represent a hierarchy you won't
use Relationships, you'll use a folder tree for example. The proposal
doesn't address hierarchies because it is not a problem and is already
quite easy to do in the ZODB whereas relationships are not.

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

_______________________________________________
For more information about ZODB, see the ZODB Wiki:
http://www.zope.org/Wikis/ZODB/

ZODB-Dev mailing list  -  ZODB-Dev at zope.org
http://mail.zope.org/mailman/listinfo/zodb-dev