Take a look at archetypes on Plone.org, and download a version from
sf.net.

Look in particular at the ReferenceEngine, based on the catalog, and
note that there have been implementation changes, and there's a new
beta version.

Ben Saller and Kapil Thangavelu were part of the team responsible for
Archetypes.

--r.

On 2 Aug 2004, at 12:46, Santi Camps wrote:


<excerpt>Hi all,


I've been developing database oriented applications for about 10
years, using zope with Relation DDBB for one year and a half, and just
one year using Zope with ZODB in my applications.   At this point, I
can see a lot of advantatges of use ZODB with Zope, but there are some
points where the relational model was more useful to me. In fact, the
main problem in my applications are relationships.   In a relational
world, you can specify relations using foreign keys, and also say what
action should be done on delete or on update (no action, set null,
restrict, cascade, set default).   This is very useful developing
business oriented applications. Using ZODB some of these relations can
be done using containment:   If A contains B, this is the same of
having a relation "1->N on delete cascade"

Another case is to use a Relation Manager.   I've implemented and
object Relation that is deleted when some of the two related objects
are (using manage_beforeDelete).  This is the same that a relation "M
-> N on delete cascade"

The third case I've been implemented, and the one giving me more
problems, is to have a property referencing another object (path or
UID).  If the referenced object is dropped, the referer has problems


I work a lot with ZCatalogs, using one catalog for each meta_type of
objects, so for me catalogs are the most similar thing to a "Table".  
I'm thinking that could be very useful to implement some basic
referencial integrity in ZCatalogs.   Just being able to define
primary keys and some simple types of foreign keys we will have on
Zope the best of two worlds.   Seeing code of ZCatalog product it
seems not to be very difficult to implement, adding some validations
on catalog_object and uncatalog_object methods.   Of course, all these
should be optional.   I no Primary Keys neither Foreign Keys are
defined, catalogs should work exactly like until now.


What do you think about this ?  If nobody convince me that this is a
stupid work, I will try to implement it.   In this case, what's the
better way to provide the code ?  A patch for ZCatalog ?  Or a new
Product IntegrityZCatalog inheriting from ZCatalog ?


Thanks


Santi Camps


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</excerpt>—————————————————————

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