[Openflow-dev] Re: Datas in a database (was Re: [Openflow-dev] zpt)

[<jm...@te...>]

Hi,

finally I start to understand DBObjects.

A bit hard... The conclusion is that it is possible to implement objects
in a database (in our case, 2 classes: instances and workitems). If
someone (me?) read this on the future, I hope this will help:


It seems that with DBObjects:

- each class must have a predefined set of attributes
- these attributes aren't properties (DBObjects aren't
derived form PropertyManager).

So it's clear that an instance can't be a DBObject, because it's not
generic enough.

However there is FolderishDBObjects, which can contain DBObjects, so it
would be possible to implement properties (one DBObject per property).

Well, from the point of view of database connection, dynamic tables
creation, I have no idea of how factible it is (DBObject requires postgree
sql and the correspondente ZopeDA, and I haven't installed it).

So this is too much work for the moment, I'll keep on using the system I
have now :-)





On Wed, 25 Sep 2002, Vincenzo Di Somma wrote:

> On Wednesday 25 September 2002 18:15, Juli=E1n Mu=F1oz wrote:
> > On Wed, 25 Sep 2002, Vincenzo Di Somma wrote:
> > > > I would be very much interested in features like separating the dat=
as
> > > > of the Openflow (instances and workitems) in a database.
> > >
> > > Any proposal about that ?
> >
> > Using something like:
> >
> > http://www.zope.org/Members/srichter/Products/DBObjects
> > http://sf.net/projects/modeling
> >
> > But reading the first one has given me a gread headache. It's a complex
> > topic.
> >
> > Well from what I read from DBOBjects, it seems to be convenient to have=
 a
> > trace of the object in the zodb.
> >
> > You put the database adapter on the Openflow, and it regenerates the
> > object structure.
> >
> > Then, you work transparently.
> >
> > One point would be: if you delete the openflow, the objects would not b=
e
> > deleted from the database.  If you replace the openflow with and upgrad=
e,
> > it will still use the objects on the database, and will not alterate th=
em.
>
> We hope to fix the interfaces NOW :) So for the next release it will be v=
ery
> very easy to upgrade running OpenFlow objects, your product will be very
> useful :)
>
> > Well, I don't know, maybe a simpler solution would be possible, but, ho=
w
> > would you attach a property to an instance ? All seem to point to
> > something like this.
>
> I prefer instead to use the standard zope property manager properties or
> instantiate custom o standard objects in the process instance, but if in =
your
> experience you`ve found it not confortable we can try to find another
> solutions. However when I need interaction between a process instance and=
 one
> or more RDMS tables I store the primary keys in the instance and I use th=
em
> to retrive information form the DB.
>
> >
> >
> > Just ideas, for the future :-)
>
> Thanks a lot  :)
> =09Vincenzo.
>
>
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Saludos de Juli=E1n
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