diff --git a/grouper-subject-identifier b/grouper-subject-identifier
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+
+Chris Hyzer  12 hours ago
+at penn users who can log in have a pennkey which for me is mchyzer.  we also all have a pennid which is the IDM id.  mine is 10021368.  The pennkey can change, so that is not our subjectid.  the pennid doesnt change but sometime we have dupes and need to merge.  the pennid is our subjectId
+
+Chris Hyzer  12 hours ago
+10021368 is not based on name, so it is considered opaque
+
+Beth Halsema  11 hours ago
+Purdue University's unique ID is a ten-digit number that is not based on the name.  It can change as the result of a demographic correct/incorrect matching.
+
+Chris Hyzer  11 hours ago
+i think that sounds right for subjectid :slightly_smiling_face:
+
+Chris Hyzer  11 hours ago
+if you have a process for merging, you can call the member change subject web service, or it could be a manual process to see what grouper has and delete one or call member change subject via gsh.  At penn we generally just ignore this case and let it shake out (new pennid gets all the basis stuff automatically, the only pennid just goes away).  But if someone had ad hoc memberships the member change subject call will fix that
+https://spaces.at.internet2.edu/display/Grouper/Member+change+subject