Re: [Modeling-users] N-tier development and modeling

[Ernesto R. <er...@si...>]

Hi,

although this message does not respond exactly to the questions exposed =
here, I just wanted to comment what we do.

As with pyro, we designed our own protocol on top of  XMLRPC, that is, =
objects and other data (None, DateTime) may be transmitted from server =
to client for whichever purpose. The client has a collection of 'dump' =
objects, in our words ObjectProxies, and nearly every call is a =
client-server-client transaction. Business logic resides on the server. =
The database can reside on another machine, of course. This is not very =
distributed, but it's a 3-tier architecture. We are still developing, so =
actually we are not in production phase. (In the future we may switch to =
pyro and/or Corba).

On the other hand, modeling is able to run at once different models on =
differen servers, and with the future optimistic locks, the same model =
could run on several machines.

In each way, if you work in a distributed environment, the =
implementation of an object will run on one or more 'server' machines, =
and the 'clients' will hold some proxies to these objects. All method =
calls not treated locally, will be send to the server. If you do not =
want to call the remote object, whenever an attribute is accessed, you =
can implement a proxy initialization which requests and stores locally =
all object attributes, or define a method in your framework (as we did), =
which requests a collection of attribute values for some objects (as a =
batch).


Best regsards
Erny

----- Original Message -----=20
From: "John Lenton" <jo...@vi...>
To: "Modeling users' mailing list" =
<mod...@li...>
Sent: Monday, March 15, 2004 2:00 PM
Subject: Re: [Modeling-users] N-tier development and modeling


> Sender: John Lenton <jo...@ma...>
>=20
> On Sun, Mar 14, 2004 at 02:37:06PM +0100, Sebastien Bigaret wrote:
> > I must say all this is really interesting. I unfortunately do not =
have
> > the time to investigate such things deeper, but i'm really =
interested in
> > a distributed layer. Had a very quick look at pyro, seems compact =
and
> > clean. If any of you experiment in this direction I'd like to hear =
from
> > the details, problems etc. As far as I can understand things, it =
seems
> > that Tom and John are speaking about similar things, if not the =
same.
> >=20
> >   BTW about weakrefs and pickle, I can effectively confirm that =
weakrefs
> >   are used, mainly in objects (which hold a weakref to their EC) and =
in
> >   to-many faults (AccessArrayFaultHandler) which for technical =
reasons
> >   hold weakref of the object referencing them.
>=20
> I've been thinking about this a bit (`in background', if you will),
> and now I am of the opinion that actually using pyro on
> editingcontexts and modeling objects is the wrong way to do this; I
> think proxy classes (via overriding CustomObject?) is probably a saner
> way to go. You probably don't want to shuttle your modeling objects
> anyway: what you're wanting to distribute is the data, i.e. the result
> of e.g. getFirstName, and possibly (although I doubt it) the effect of
> setFirstName. Not the object itself; that would imply you are
> distributing your business logic. I'll try to set up an example using
> cimarron, so you can see what I mean.
>=20
> > John: after a quick search I was not able to find any =
english-written
> > resources about papo and cimarron, is this available somewhere?
>=20
> papo is https://papo.vialibre.org.ar, but as you noted it's in
> spanish. cimarron you can find in papo's savannah cvs; I'm afraid it's
> lacking documentation and examples, and probably isn't much use
> without a bit of handholding. However, it being a framework, we've
> tried to keep it in english, so at least running pydoc on the files in
> Generic/ should provide some insight. Consider it 'pre-alpha', because
> it is.
>=20
> --=20
> John Lenton (jo...@vi...) -- Random fortune:
> "In the long run, every program becomes rococo, and then rubble."
> -- Alan Perlis
>=20
>=20
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