Comparing two models for differences

I want to write a unit test that does the following:
     1. Read a MOF model into an extent using XmiReader
     2. Write the model to a SSM file using my "SSM writer".
     3. Read the SSM file back into another extent using my "SSM reader".
     4. Write the model to another SSM file using the "SSM reader" again.
     5. Verify that steps #2 and #4 result in identical files using
        the unix "diff" command.

(Note: "SSM" is the temporary name for the concrete textual syntax that 
I am developing).

Currently, I am doing steps #1-#4 automatically, but I have to manually 
inspect the results of "diff" myself. I am getting diffs that look like 
the one below. The problem is basically that MDR is giving me the "root 
nodes" in an indeterminate order. Obviously, that is not incorrect, but 
it would be nice if MDR would at least provide "best effort" in 
preserving the ordering of _all_ collections, whether they are 
explicitly marked isOrdered=true or not. In other words, treat all 
multiplicities as though isOrdered=true. What do you think?

Another similar use case:

Currently, you can't use XMI files as "golden files" in unit tests for 
the same reasons I can't use diff to compare my "SSM" files (perhaps 
among other reasons, such as the way xmi.id's are generated).

Another similar use case:

Lets say that I'm using MDR to manipulate XMI files. I want to store the 
XMI files in version control with CVS. In that case, "best effort" 
preservation of the ordering of unordered collections is necessary; 
otherwise, CVS and "diff" will likely report many more differences (and 
conflicts) than actually exist. I know that Novosoft implemented 
something special in the XMI reader/write to handle this scenerio, 
although maybe they only made an effort to preserve the xmi.id's.

Thanks,
Brian

Example diff (notice that the only difference is that the packages 
PrimitiveTypes and CorbaIdlTypes are reversed in order):

-package PrimitiveTypes
+package CorbaIdlTypes
  {
-   tag "*tag" : javax.jmi.packagePrefix = 'javax.jmi' on ::PrimitiveTypes
-   primitive type Boolean
-   primitive type Integer
-   primitive type Long
-   primitive type Float
-   primitive type Double
-   primitive type String
+   tag "*tag" : javax.jmi.packagePrefix = 'javax.jmi' on ::CorbaIdlTypes
+   primitive type CorbaOctet
+   primitive type CorbaShort
+   primitive type CorbaUnsignedShort
+   primitive type CorbaUnsignedLong
+   primitive type CorbaUnsignedLongLong
+   primitive type CorbaLongDouble
+   primitive type CorbaString
+   primitive type CorbaChar
+   primitive type CorbaWChar
  }

  package Model
@@ -322,17 +325,14 @@
     }
  }

-package CorbaIdlTypes
+package PrimitiveTypes
  {
-   tag "*tag" : javax.jmi.packagePrefix = 'javax.jmi' on ::CorbaIdlTypes
-   primitive type CorbaOctet
-   primitive type CorbaShort
-   primitive type CorbaUnsignedShort
-   primitive type CorbaUnsignedLong
-   primitive type CorbaUnsignedLongLong
-   primitive type CorbaLongDouble
-   primitive type CorbaString
-   primitive type CorbaChar
-   primitive type CorbaWChar
+   tag "*tag" : javax.jmi.packagePrefix = 'javax.jmi' on ::PrimitiveTypes
+   primitive type Boolean
+   primitive type Integer
+   primitive type Long
+   primitive type Float
+   primitive type Double
+   primitive type String
  }