when using UMIL with sql server then the script will break when dropping column, mentioning an error like this in UMIL.

Msg 5074, Level 16, State 1, Line 1
The object 'DF_RproleIsClo_4BCC3ABA' is dependent on column 'IsClosed'.
Msg 4922, Level 16, State 9, Line 1
ALTER TABLE DROP COLUMN IsClosed failed because one or more objects access this column.

This happens because of "DEFAULT" constraints which is always the case when not adding one specifically
see http://stackoverflow.com/questions/314998/sql-server-2005-drop-column-with-constraints

solution is to drop default constraint before dropping column. in Oracle this is simply "DROP COLUMN xxx CASCADE CONSTRAINTS" but in SQL server the only solutions seems to be a T-SQL script.