<br/>
Describing your Simulated Platform
-==================================
+##################################
+
+The goal of SimGrid is to run an application on a simulated platform.
+For that, you have to describe **each element of your platform**, such
+as computing hosts, clusters, each disks, links, etc. You must also
+define the **routing on your platform**, ie which path is taken
+between two hosts. Finally, you may also describe an **experimental
+scenario**, with qualitative changes (e.g., bandwidth changes
+representing an external load) and qualitative changes (representing
+how some elements fail and restart over time).
+
+You should really separate your application from the platform
+description, as it will ease your experimental campain afterward.
+Mixing them is seen as a really bad experimental practice. The easiest
+to enforce this split is to put the platform description in a XML
+file. Many example platforms are provided in the archive, and this
+page gives all needed details to write such files, as well as some
+hints and tricks about describing your platform.
+
+On the other side, XML is sometimes not expressive enough, in
+particular for large platforms exhibiting repetitive patterns that are
+not simply expressed in XML. In practice, many users end up
+generating their XML platform files from some sort of scripts. It is
+probably preferable to rewrite your XML :ref:`platform using the lua
+scripting language <platform_lua>` instead. In the future, it should
+be possible to describe the platform in python or directly in C++, but
+this is not possible yet.
+
+As usual, SimGrid is a versatile framework, and you should find the
+way of describing your platform that best fits your experimental
+practice.
+
+
+
+
+.. LocalWords: SimGrid
