Re: [Qscada-developers] Hi all

[Jovan K. <cho...@gm...>]

Hi,

On 3/19/07, Reza Azizi <azi...@gm...> wrote:
> OK
>  as you know there is some limitation on showing real time value on web.
> because of HTTP limitation. HTTP is a one way protocol.
> by using ajax we can have more chance to show user, new data.
> but by making network and web server busy.

Yes, that's true, the server will be busy. That will depend on the
number of clients and assuming that the beside the web server for
serving the ajax hmi, the whole qscada system will work on the same
machine it can be a problem.
When I proposed the ajax hmi, I was guided by "no refresh" web page
not thinking much of the things that are going on behind the scenes.
Thanks for reminding us about that.

> for web system i recommend tomcat webserver with JSP for presentation
> and Servlet for business logic.
> tomcat work well with mysql and linux.

I've read some articles on JSP and Java Servlets, but I've never
worked with them.
If we can reduce the network load and do some custom graphic drawing
(for gui components in the hmi representing the parts of the plant),
why not.

Can you give us, your vision of a web based hmi?

> you say that you are in architectural design phase.
> it means that your analyze and requirement gathering must be complete.
> is it true?

Well, basicly we have this two documents listed below and
the discussions made here on the list.

http://qscada.sourceforge.net/docs/vd_ps_02_draft.pdf
http://chombium.awardspace.com/files/qscada/prop01.pdf

I wanted to put all the things together in one document that
will describe the whole architecture. At the time this things
happened we were four: me, Paolo, James and Ian. There
are also some "want to learn" (sorry for this title ;) ) people
on the list, that were asking some questions on SCADA systems
and protocols.

Since the group is growing I think we shoud hear our new members,
so, everybody, don't be shy tell us what you think, share with us
your vision of this project.
Tell us what do you expect from it and what do you want this project
to be able to do for you.

BR, Jovan