Index: 02_data.html
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--- 02_data.html	(revision 4525)
+++ 02_data.html	(revision 4526)
@@ -207,6 +207,13 @@
 unique ID ("symbol UID"), and an instantiation-time cschem generated
 unique ID for each instance ("instance UID", the uuid field of the direct group).
 
+<p>{des2:82}
+Groups also have an src_uuid field, which is used to track original sources.
+A newly created group has NIL (empty) src_uuid. Any copy of the group
+(e.g. an instance of the a library symbol on a sheet) will have src_uuid
+filled in with the src_uuid value of the source group, or if that was NIL,
+with the instance uuid of the source group.
+
 <p>{des2:53}
 When an existing instance is moved within the sheet, renamed, its
 attributes changed, it retrains instance UID. When the instance is