--- a/Comm.lua	Sat Apr 14 10:12:06 2012 -0400
+++ b/Comm.lua	Sun Apr 15 14:42:14 2012 -0400
@@ -25,7 +25,7 @@
 
 local function SendMessage(str)
     --commlib:SendCommMessage("BSKADDON",str,"GUILD")
-    commlib:SendCommMessage("BSKADDON",str,"RAID")
+    commlib:SendCommMessage("BSKADDON"..commversion,str,"RAID")
 end
 
 local function Send(handler,message)
@@ -90,8 +90,29 @@
     Comm[packet[1]](Comm,packet[2],sender,isloop)
 end
 
+alertlist = {}
+local function OnOlderCommReceived(prefix, message, distribution, sender)
+    if not alertlist[sender] then
+        printf("Received communication from %s, who is using an older version of the addon; ignoring",sender)
+        alertlist[sender]=true
+    end
+end
+
+local function OnNewerCommReceived(prefix, message, distribution, sender)
+    if not alertlist[sender] then
+        printf("Received communication from %s, who is using a newer version of the addon; ignoring",sender)
+        alertlist[sender]=true
+    end
+end
+
 function InitializeComm()
-   commlib:RegisterComm("BSKADDON",OnCommReceived)
+    for i = 0,commversion-1 do
+        commlib:RegisterComm("BSKADDON"..i,OnOlderCommReceived)
+    end
+    commlib:RegisterComm("BSKADDON"..commversion,OnCommReceived)
+    for i = commversion+1,commversion+5 do -- some sensible number
+        commlib:RegisterComm("BSKADDON"..i,OnNewerCommReceived)
+    end
 end
 
 function DeinitializeComm()

--- a/Core.lua	Sat Apr 14 10:12:06 2012 -0400
+++ b/Core.lua	Sun Apr 15 14:42:14 2012 -0400
@@ -6,7 +6,7 @@
 -- (*) all actions should reference the player list rather than player names
 -- (?) player entries should persist as long as any list or change references
 -- (*) lists store number slots rather than flat indexing
--- ( ) database and comm versioning
+-- (*) database and comm versioning
 -- (_) limited communication - everyone trusts the loot master
 -- (*) single user + admin gui (manual suicides)
 -- (*) single user + admin gui (master loot)
@@ -38,6 +38,9 @@
 -- 4) table.remove() works ok if reverse iterating, terrible at anything else
 -- 5) pairs() does not have a guaranteed iteration order
 
+dbversion = 1
+commversion = 1
+
 function OnInitialize()
 
     debug = true
@@ -49,6 +52,9 @@
     --optionsFrame = LibStub("AceConfigDialog-3.0"):AddToBlizOptions("bsk", "bsk")
 
     admin = db.profile.admin
+    if not db.profile.dbversion or db.profile.dbversion < dbversion then
+        UpgradeDB()
+    end
 
     local HandlePassThrough = function(...) HandleCommand(...) end
     bsk:RegisterChatCommand("bsk", HandlePassThrough)
@@ -209,3 +215,13 @@
     }
 }
 
+function UpgradeDB()
+    local mydbver = db.profile.dbversion or 0
+
+    if mydbver == 0 then -- difference between 0 and 1 is whether this field is present
+        db.profile.dbversion = 1
+        mydbver = 1
+    end
+
+
+end