source: branches/fscctrl_safety_limits/www/smartfact/struct/help-introduction.page@ 18679

Introduction
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The idea of SmartFACT++ is simple. A backend (<I>smartfact</I>) updates some
data-files continously which can then be retrieved from a web-server
and the data is displayed in your browser. To keep the network traffic
low the data is not encapsulated in html, but transmitted <I>as is</I>.
A JavaScript, running client side, <I>i.e.</I> on the machine running
the browser is then creating the html around it dynamically which is then
displayed by the browser. The backend writing the data-files can be basically
everything. In case of FACT it is a program called <I>smartfact</I> which
subscribes to all dim-services in the dim-network which are needed.
Whenever a service is updated, the corresponding files are also updated.
The disadvantage is that it is difficult to mix information which is 
not updated together in a single file and display it on a single page.
This, <I>e.g.</I>, means that a file which is only updated every two 
hours (because new information is only available every two hours) cannot
reasonably store information which can change every minute, <I>e.g.</I>
general warnings. Every page is restricted to reload a single file, to 
keep network traffic low. A simple solution would be a php which concatenates 
information before the information is transfered, but this is (not yet?)
available. Consequently, all pages which are not updated frequently or
are guranteed to be updated frequently will not show fats updateing
information as warning. Some pages, <I>e.g.</I>, the main page are
updated once every seconcd or few seconds rather than updated
event-driven by the reception of a new service. These pages will then
show informations like the current warning status of the system.

The page description is reloaded whenver a page has been clicked to
avoid a lot of network traffic at startup. The disadvantage is a little
network traffic (in the order of a few hundred bytes) whenever a page
is changed.
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