Subject: Re: MW minutes
Date: Mon, 02 Aug 1999 18:26:44 +0200
From: Kris KOSTRO <Kris.Kostro@cern.ch>
Organization: CERN
To: Alessandro RISSO <Alessandro.Risso@cern.ch>,
     Franck DI MAIO <Franck.Di.Maio@cern.ch>,
     Marc Vanden Eynden <Marc.Vanden.Eynden@cern.ch>,
     Vito BAGGIOLINI <Vito.Baggiolini@cern.ch>

The minutes from the last meeting - as good as my notes and memory are a
week later ...

Minutes from the Middleware meeting Mo. 26 of June 1999

Present: Alessandro, Kris, Marc, Vito
Excused: Franck away on leave

1. Status and distribution of the requirements document.

Marc is still waiting for comments on URD, especially qualifiers. So far
only comments from Kris received. Marc will publish the new version mid
of the week. Last comments are awaited for Friday.

2. Remote Device Model and two-tier versus three-tier architecture.

This subject was the most hotly discussed. There is consensus that
three-tier architecture is the best suited but there are divergences as
for what it actually means. In fact there are three aspects of it which
have been discussed:
- Middleware has to provide middle tier services so that equipment
servers can be easilly deployed and services such as persistency,
security etc. can be offered to the servers in an OO manner (i.e. as
interfaces). (Kris and Vito) This area is addressed by EJB and CORBA
components.
- In the three-tier architecture imagined by Vito the middle tier would
provide, in addition to generic services mentioned above, specific
"business components" implementing controls logic for components such as
beam line. The first tier would be essentially restricted to GUI. The
general comment was that such architecture, although very modern cannot
be imposed everywhere. It should be however possible to deploy such
architecture with the Middleware. Specific controls components are not
subject of the MW project.
- Because resources in Front-Ends are limited there is a general feeling
that a three-process architecture with a GUI client (first tier), a
proxy equipment server in a workstation (second tier) and an resource
server (third tier) would be the most interesting. On the other hand
this architecture should not limit the performance (by store and
forward) and we also requested that all services should be implemented
in Front Ends (symmetricity).

Preliminary conclusions from the discussions:

1) The Middleware should offer generic services in the middle tier such
as persistency or security. The goal is to make available these services
everywhere (including F-E) but it could be that some of them will only
be available on industry standard platforms (PC and Workstations).

2) The Middleware should provide tools and support for three-process
architecture in which an equipment proxy server or equipment group
server can be easilly configured on an industry standard platform. In
this architecture the third tier (resource tier) would be very simple
and most of the equipment logic would be implemented in the middle tier.

3) The Middleware should allow for architecture in which all of the
equipment logic is implemented by the middle tier and first tier is
reduced to a GUI client.

3. Concrete investigations.

It has been proposed to pick out one of the most important aspects of
the middleware which is the subscription service and investigate the
feasibility of it wit CORBA and with MOM.

- Alex and Kris will investigate tools and services available for
subscription in CORBA
- Marc and Vito will do the same for MOM (which ?)

Next meeting We 4 Aug. 9:00 at SL

I will be away Tu morning.

Kris
-