Index: trunk/doc/user/03_data/index.html
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--- trunk/doc/user/03_data/index.html	(revision 13601)
+++ trunk/doc/user/03_data/index.html	(revision 13602)
@@ -114,6 +114,20 @@
 
 <h3> 3.4. file formats</h3>
 <p>
+pcb-rnd operates on an in-memory data tree of the board while it is being edited.
+The in-memory data tree can not be dumped in a file without conversion: loading
+any file means converting the given file format to the in-memory representation
+and saving from memory to any file format is just another conversion.
+
+<p>
+Lossless save/load round trips for all pcb-rnd features are guaranteed
+only when using the latest version of the native formats. The reason is
+that the native formats are always upgraded to support all features of
+the in-memory data model. It is possible (but not recommended) to use
+older versions of the native formats to retrain compatibility with older
+versions of pcb-rnd.
+
+<p>
 The <i>native</i> file formats of pcb-rnd are:
 <ul>
 	<li> lihata board for PCBs
@@ -122,12 +136,6 @@
 </ul>
 
 <p>
-Lossless save/load round trips for all pcb-rnd features are guaranteed
-only when using the latest version of the native formats. It is possible
-(but not recommended) to use older versions of the native formats to
-retrain compatibility with older versions of pcb-rnd.
-
-<p>
 Non-native file formats are called <i>alien</i> formats. pcb-rnd supports
 a large variety of alien formats, but lossless save/load round trips are
 not guaranteed when alien formats are used. The code will always do its best