Compare the attribute extensions of two DOFObjectOIDs, excluding the base ID. 
- Note
 - If one parameter is NULL, it is considered less than the other. If both are NULL, they are considered equal. 
 
- Parameters
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- Returns
 - Zero if exact match. 
 
- 
Positive value if oid1 > oid2. 
 
- 
Negative value if oid1 < oid2.