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<DIV><FONT color=#0000ff size=2 face=Arial>May be the discussion goes beyond my
understanding, in which case sorry for my noise. Where I need a value distinct
from all other values (such as a no-value), I prepare an empty struct type and
export one single instance of this struct together with its predicate (and
nothing else)</FONT></DIV>
<DIV><FONT color=#0000ff size=2
face=Arial>Jos<BR><BR></FONT></DIV></BODY></HTML>