In the standard installation of CMS Fiona, the preview is delivered by the Portal Manager. From version 6.6 of the CMS you can alternatively integrate a Rails application as the preview, so that the editors can view the content they create in the layout of the Rails application..
With websites realized as rails applications, the web pages are delivered dynamically. The Rails server generates the requested pages on-the-fly and uses for this the content currently present in its database. If the databases of the editorial and the live system are synchronized, your website will always be highly up-to-date. As an option, caching mechanisms might be used to reduce the system load.
Releasing a document in the editorial system causes this document to be published immediately. The export facilities of the CMS are not required if the content is delivered by the Rails server. Accordingly, layout files are not required in the CMS.
If a Rails application is used for previewing the content, two servers are used, one for the GUI pages (Trifork) and one for the preview pages (Mongrel). The servers communicate with each other. To the client, the servers need to appear as one because for security reasons most browsers do not permit XSS.
For this reason an Apache HTTP server is placed as a reverse proxy in front of the servers mentioned above.
Section Integrating the Rails preview into the GUI explains how the Rails preview can be enabled.