Here is a snippet of my class mapping file.
Code:
<many-to-one name="Sector" class="Sector,MyDll" not-null="true">
<column name="PrimarySSC"/>
<column name="Language"/> <!-- Don't save this -->
</many-to-one>
<many-to-one name="Language" column="Language" class="Language,MyDll" not-null="true"/>
Since this isn't a property there is no update="false" option. The language is there to keep track of what language is used in the object and for all related objects. So ideally the language column is shared by the class and its children.
Let me know if you need more information.