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 <h3> 3.4. file formats</h3>
-<h3> 3.4.1 board formats</h3>
-<ul> 
-    <li> lihata
-    <li> legacy pcb
-    <li> kicadl
-    <li> kicad
-    <li> eagle
-    <li> autotrax
+<p>
+The <i>native</i> file formats of pcb-rnd are:
+<ul>
+	<li> lihata board for PCBs
+	<li> lihata subcircuit for footprints
+	<li> lihata based pcb-rnf-conf for configuration data
 </ul>
-<h3> 3.4.2 footprint formats</h3>
-<h3> 3.4.2 pcb-rnd import </h3>
-<h3> 3.4.2 pcb-rnd export </h3>
+
+<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
+to get good results, but different alien formats have different features,
+and most of them can not fully capture all features pcb-rnd offers.
+
+<p>
+Some alien formats are implemented as io_ plugins and are accessible
+as normal board (and footprint) file formats directly from the load/save
+infrastructure and footprint library. These formats are trying to capture
+all details of the board (or footprint) and are usually close to
+producing lossless save/load round trips. 
+
+<p>
+Other alien formats are supported through import_ or export_ plugins.
+These formats do not capture enough aspects of a board (or footprint) to
+be used as a full load or save, round trip of any sort is impossible.
+
+<p>
+Typical export example is render outputs: png, ps, gerber are all
+export_ plugins: they export one aspect (geometry and sometimes layering)
+of the board, but do not export other aspects such as connections,
+subcircuits or padstack structure. Lacking that information, the exported
+board can never be loaded as a board from png, ps or gerber.
+
+<p>
+Typical import example is netlist (or schematics): it deals with one aspect
+of the project, connection info, and lacks any phyiscal information such
+as geometry or layers. It is possible to import one aspect of the design from
+a netlist (or schematics), but it is not possible to reconstruct a full board
+using only the netlist information.
+
+<p>
+<img src="../../developer/bridges/bridges.svg" alt="a map of pcb-rnd format support">
+
+<p>
+For a detailed list of formats, please refer to the appendix.
+(TODO: link an autogenerated list)
+