Radiant is a free software

Free software

Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...

 content management system

Content management system

A content management system is a system providing a collection of procedures used to manage work flow in a collaborative environment. These procedures can be manual or computer-based...

 written in Ruby

Ruby (programming language)

Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. Ruby originated in Japan during the mid-1990s and was first developed and designed by Yukihiro "Matz" Matsumoto...

 created and designed by John W. Long as a Ruby on Rails

Ruby on Rails

Ruby on Rails, often shortened to Rails or RoR, is an open source web application framework for the Ruby programming language.-History:...

 web application.

Radiant has a core with a limited set of functionality (compared with other systems). With over 200 extensions in the extension registry it can be adapted for various uses. All the content is stored inside a database. It is possible to use MySQL

MySQL

MySQL officially, but also commonly "My Sequel") is a relational database management system that runs as a server providing multi-user access to a number of databases. It is named after developer Michael Widenius' daughter, My...

, PostgreSQL

PostgreSQL

PostgreSQL, often simply Postgres, is an object-relational database management system available for many platforms including Linux, FreeBSD, Solaris, MS Windows and Mac OS X. It is released under the PostgreSQL License, which is an MIT-style license, and is thus free and open source software...

 or SQLite

SQLite

SQLite is an ACID-compliant embedded relational database management system contained in a relatively small C programming library. The source code for SQLite is in the public domain and implements most of the SQL standard...

. Radiant depends, like every Ruby on Rails application, on the installed adapters for the database.

It is distributed via a separate download or installable with RubyGems

RubyGems

RubyGems is a package manager for the Ruby programming language that provides a standard format for distributing Ruby programs and libraries , a tool designed to easily manage the installation of gems, and a server for distributing them. It is analogous to EasyInstall for the Python programming...

.

Two PHP ports of Radiant CMS are available as Frog CMS

Frog CMS

Frog CMS is an open source content management system originally developed by Philippe Archambault. The design decision taken from its start was to use PHP5 as the language for the software, along with a MySQL database backend, although it also has support for SQLite...

 and Wolf CMS

Wolf CMS

Wolf CMS is a content management system and is Free Software published under the GNU General Public License v3. Wolf CMS is written in the PHP programming language...

.

Design

Radiant projects are based on 3 elements: Pages, Snippets and Layouts.

Pages:
The content of every page is stored in Pages. Every page has specific attributes and content. For example, if Radiant is used as a blog, all blog entries are Pages inside the Radiant system. They can be arranged hierarchically to reflect the actual structure of the content.

Snippets:
Snippets are essentially just small parts of code that can be reused everywhere in the project and make page creation easier.

Layouts:
To define the general look of a page layouts are used. Upon page creation, a layout can be attached to that page to define a frame for this Page to be inserted in.

Radius Template Language

Inside a Page, Layout or Snippet, Radiant offers a special templating language, called Radius, that allows a user to easily access data, loop through content, or make conditional checks.

Radius tags are XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

-like tags that start with "r:".

Here is an example of Radius tags inside page layout: