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diff --git a/indra/lib/python/indra/ipc/compatibility.py b/indra/lib/python/indra/ipc/compatibility.py
new file mode 100755
index 0000000000..b9045c22f3
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+++ b/indra/lib/python/indra/ipc/compatibility.py
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+"""\
+@file compatibility.py
+@brief Classes that manage compatibility states.
+
+$LicenseInfo:firstyear=2007&license=mit$
+
+Copyright (c) 2007-2009, Linden Research, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+$/LicenseInfo$
+"""
+
+
+"""Compatibility combination table:
+
+    I   M   O   N   S
+    --  --  --  --  --
+I:  I   I   I   I   I
+M:  I   M   M   M   M   
+O:  I   M   O   M   O
+N:  I   M   M   N   N
+S:  I   M   O   N   S
+
+"""
+
+class _Compatibility(object):
+    def __init__(self, reason):
+        self.reasons = [ ]
+        if reason:
+            self.reasons.append(reason)
+        
+    def combine(self, other):
+        if self._level() <= other._level():
+            return self._buildclone(other)
+        else:
+            return other._buildclone(self)
+    
+    def prefix(self, leadin):
+        self.reasons = [ leadin + r for r in self.reasons ] 
+    
+    def same(self):         return self._level() >=  1
+    def deployable(self):   return self._level() >   0
+    def resolved(self):     return self._level() >  -1
+    def compatible(self):   return self._level() >  -2
+    
+    def explain(self):
+        return self.__class__.__name__ + "\n" + "\n".join(self.reasons) + "\n"
+        
+    def _buildclone(self, other=None):
+        c = self._buildinstance()
+        c.reasons = self.reasons
+        if other:
+            c.reasons = c.reasons + other.reasons
+        return c
+        
+    def _buildinstance(self):
+        return self.__class__(None)
+
+#    def _level(self):
+#        raise RuntimeError('implement in subclass')
+
+
+class Incompatible(_Compatibility):
+    def _level(self):
+        return -2
+
+class Mixed(_Compatibility):
+    def __init__(self, *inputs):
+        _Compatibility.__init__(self, None)
+        for i in inputs:
+            self.reasons += i.reasons
+                    
+    def _buildinstance(self):
+        return self.__class__()
+        
+    def _level(self):
+        return -1
+
+class _Aged(_Compatibility):
+    def combine(self, other):
+        if self._level() == other._level():
+            return self._buildclone(other)
+        if int(self._level()) == int(other._level()):
+            return Mixed(self, other)
+        return _Compatibility.combine(self, other)
+
+class Older(_Aged):
+    def _level(self):
+        return -0.25
+    
+class Newer(_Aged):
+    def _level(self):
+        return 0.25
+
+class Same(_Compatibility):
+    def __init__(self):
+        _Compatibility.__init__(self, None)
+    
+    def _buildinstance(self):
+        return self.__class__()
+        
+    def _level(self):
+        return 1
+
+
+
+