Sorry, typo: I wrote: > as in X>Z,Y>Z,X?Z but meant X>Z,Y>Z,X?Y of course. As a Hasse diagram: X Y \ / \ / Z Not to be confused with X=Y>Z: X=Y | | Z More complex example: A>B>C>D,A>E=F>D: A / \ B \ | E=F C / \ / D Jobst