Index: trunk/doc/developer/io_lihata_ver.html
===================================================================
--- trunk/doc/developer/io_lihata_ver.html	(revision 19108)
+++ trunk/doc/developer/io_lihata_ver.html	(revision 19109)
@@ -64,6 +64,8 @@
 	New layer group types PCB_LYT_DOC and PCB_LYT_MECH are handled on load
 	and save.
 	<p>
+	Load and save purpose field in layer groups and bound layers.
+	<p>
 	The layer visibility bit is not saved any more - it was reset after load so
 	it only added noise to the file.
 
Index: trunk/doc/developer/lihata_format/comm_data.lht
===================================================================
--- trunk/doc/developer/lihata_format/comm_data.lht	(revision 19108)
+++ trunk/doc/developer/lihata_format/comm_data.lht	(revision 19109)
@@ -79,6 +79,7 @@
 								desc={only for bound layers: try to bind to this type of layer on the host board}
 								sy:children {/lht_tree_doc/comm/layer_mask/children}
 							}
+							ha:purpose    = { valtype=integer; ver={>=6} desc={only in bound layers: match layer group purpose}}
 							ha:combining {
 								ver={>=2}
 								desc={layer combination (compositing) flags}
Index: trunk/doc/developer/lihata_format/root_board.lht
===================================================================
--- trunk/doc/developer/lihata_format/root_board.lht	(revision 19108)
+++ trunk/doc/developer/lihata_format/root_board.lht	(revision 19109)
@@ -75,6 +75,7 @@
 										desc { a flag-list of layer type flag bits }
 										sy:children = {/lht_tree_doc/comm/layer_mask/children}
 									}
+									ha:name { valtype=string; ver={>=6} desc={purpose of layer groups (useful with mechanical/documentation groups}}
 									ha:layers {
 										type=li
 										desc { ordered list of logical layer IDs hosted by this layer group }