Index: 03_drawing.html
===================================================================
--- 03_drawing.html	(revision 561)
+++ 03_drawing.html	(revision 562)
@@ -64,13 +64,15 @@
 
 <h3> 3.1.1. Local identifier </h3>
 
-<p>{des3:10} An <i>oid</i> is an unsigned 32 bit integer. Any time a new
+<p>{des3:10} An <i>oid</i> is a signed 32 bit integer. Any time a new
 drawing object is placed on the sheet, the new drawing object's <i>oid</i> is set to
 the sheet's <i>next_oid</i> and the sheet's <i>next_oid</i> is incremented.
 
 <p>{des3:11} The <i>oid</i> value 0 means "invalid" or "unused" or "unspecified".
 Any non-zero <i>oid</i> is a valid drawing object ID. The same <i>oid</i> can not
-be attached to two different drawing objects within a sheet.
+be attached to two different drawing objects within a sheet. Only positive
+<i>oid</i> values shall be used in files or communication, negative values
+are reserved for application-internal use.
 
 <p>{des3:12} The <i>oid</i> is used for referencing drawing primitives
 within the sheet. It is meant for internal references only: external objects,