NAMESPACE column in OBJ$

Could someone explain to me what the NAMESPACE column is for in the SYS.OBJ$ table? I've been hunting around, but almost everything I've found so far has to do with OO programming, and the few web pages that have come up with that column don't actually say anything about it: it's just in some sample code.

Background: The following cursor is in the application I'm working on:

CURSOR g_get_nullable (

    i_table_name VARCHAR2,
    i_column_name VARCHAR2
) IS

    SELECT DECODE(count(*), 0, 'Y', 'N') nullable     from

        sys.ccol$ cc,
        sys.con$ c,
        sys.col$ col,
        sys.obj$ o
    where
        o.owner# = userenv('SCHEMAID')
        and o.name = UPPER(i_table_name)
        and o.namespace = 1
        and col.obj# = o.obj#
        and col.name = UPPER(i_column_name)
        and cc.obj# = o.obj#
        and cc.col# = col.col#
        and c.con#  = cc.con#
        and c.name like 'NN%' ;

I think I can just replace it with a query of USER_TAB_COLUMNS, but I'm not sure what the o.namespace = 1 does.

-- 
Jason Heinrich

--
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