Re: [school-discuss] ZIS Server (was: Project Proposal)

[Tonnesen Steve <tonnesen@cmsd.bc.ca>]

On Tue, 22 Jan 2002, Chris Hobbs wrote:

> Tonnesen Steve wrote:
> 
> >As far as demand goes, don't forget
> >that this machine isn't actually _generating_ any of this data, it is just
> >passing messages back and forth between other applications.  I don't
> >suspect that speed of the ZIS server is going to be as critical as you
> >might think.  
> >
> So based on this message and the one where you detail SIF messages, a 
> server merely acts as a gatekeeper - when a request comes in from app A, 
> the server checks it's registrations to see which app provides that 
> info. If app B is registered as the provider, does this mean that the 
> server merely tells app A where to find the info, or does the server 
> request the data from app B and then resend it to app A?

The latter.  The ZIS server is in charge of all access controls.  It can
read all data from app B, but if app A is actually a student running an
application that shows daily announcements, they will only be allowed to
view announcements intended for students.  The SIF protocol outlines 3
types of nodes:

ZIS server  - There is only one of these

Agent
Application
  These are in pairs.  The application is something like a Student
  Information System.  The agent is the program that passes messages back
  and forth between the Application and the ZIS server.

From what I understand, the Agent may have to be capable of receiving
messages that are PUSH'ed from the ZIS server, so it has to be capable of
sending out HTTPS requests as well as receiving HTTPS requests.  I think
that agents might be able to tell the ZIS server that they are PULL only
agents and the ZIS server cannot contact them directly.   It woouldn't be
necessary for a "Daily Announcements" application to have PUSH capability,
for example.  The user could just click on a Refresh button to PULL new
announcements or the application could poll for new announcements.

Steve.