replacing the old HTML user guide with a Sphinx-managed user guide
diff --git a/user_guide_src/source/overview/appflow.rst b/user_guide_src/source/overview/appflow.rst
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+######################
+Application Flow Chart
+######################
+
+The following graphic illustrates how data flows throughout the system:
+
+|CodeIgniter application flow|
+
+#. The index.php serves as the front controller, initializing the base
+ resources needed to run CodeIgniter.
+#. The Router examines the HTTP request to determine what should be done
+ with it.
+#. If a cache file exists, it is sent directly to the browser, bypassing
+ the normal system execution.
+#. Security. Before the application controller is loaded, the HTTP
+ request and any user submitted data is filtered for security.
+#. The Controller loads the model, core libraries, helpers, and any
+ other resources needed to process the specific request.
+#. The finalized View is rendered then sent to the web browser to be
+ seen. If caching is enabled, the view is cached first so that on
+ subsequent requests it can be served.
+
+.. |CodeIgniter application flow| image:: ../images/appflowchart.gif