[Zope3-Users] Re: [Zope] PEAK

[Tom Dossis]

Andreas Pauley wrote:
>>>> In an enterprise application environment (read: no website stuff), when
>>>> would PEAK be better suited and when would you rather use Zope X3?
>>
>>
> Philip has already answered the same question on the PEAK list, but I 
> thought it good to ask the opinions of the Zope community as well.

You'll probably want to consider how you need to access Zope3 - "no 
website stuff".

A quick and simple way is a fat client model.  Each client consists of 
your GUI app directly using Zope X3 and ZEO to share a central ZODB. 
However security-wise this leaves you pretty limited (exposed).  Also, I 
don't how well this would scale up with lots of clients.  If these 
issues don't effect you, then this would be a quick and easy way to go.

At the other end of the scale Zope runs an xmlrpc server.   However this 
can pretty slow and cumbersome for a demanding (intensive) GUI client app.

I'm not aware of much in the way of a middleground between the above. 
If you want a fast RMI / Object broker access to a Zope3 server, then 
you'll probably need to do this yourself.

My guess is the Zope community is larger than PEAK's so you may have a 
larger range of add on products to choose from.  However these may be 
biased toward web based apps, but this could less of an issue with Zope3.

Another consideration, is how well the persistent/component/catalog 
model suits your domain.

> 
> I'm busy working through the messageboard example in your book, that 
> ought to give me a good idea of what I can do with Zope 3 (thanks for 
> the book, the documentation for Zope 3 is a million times better than 
> that of Zope 2).
> 
> My specific project is to (firstly) re-write our current point-of-sale 
> using open-source technology.
> 
> Secondly, and probably more importantly, this project is a pilot project 
> that should establish a development environment, technology, methodology 
> etc. that could be used by the company for future similar projects.

I think you can acheive this.  Zope3 provides a consistent component 
framework from which you could develop useful client classes to to reuse 
in other projects.  For example you could build an analogous module to 
QSQL to allow generic traversal of a Zope app, including support for 
adding/deleting objects, etc.   You can also develop generic zope view 
classes (tree/list, etc) as base classes.  Something along the lines of 
QT4 Interview could make this simpler to implement.  And of course you 
could utilise Schema's for form management.

> 
> Other project specifics:
> The user interface should be a GUI (but not mouse-driven) eg, QT or GTK.
> It should interface with the existing ERP backend, and preferably any 
> other backend. The backend is currently using appservers from Progress 
> Software Corporation (a propriatary database company).

I'm not sure about the lastest version of Progress, but on Linux I think 
you may only be able to access Progress externally via ODBC, e.g. using 
the OpenLink drivers.  I don't believe Zope3 currently has an ODBC 
database adaptor.

> 
> The POS would typically be deployed in Supermarkets in Africa where 
> reliable network connectivity cannot be taken for granted. If the 
> network is down the POS station should function normally, without the 
> users or customers even being aware of any network problems. Currently 
> this is done by submitting transactions and other relevant messages to a 
> local queue, which then delivers the messages to the backend. This same 
> message queue is used when the backend wants to send messages to each 
> POS station (eg. price updates).
> 
> Reliability is also important. If the power suddenly drops the POS 
> station (typically a Linux machine) should easily be able to get back up 
> to the state it was before the power failure.

This shouldn't be an issue..

-Tom

> 
> Thats about al I can think of right now :-)
> 
> Regards,
> Andreas
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