I confess this question is rather theory-internal, but it may be very trivial for someone who follows the theoretical literature well. I am thinking of a type of constraint and want to know if such a thing has been proposed before, in the OT literature or elsewhere.
Imagine a representation where X is a root node, and i and j are features of the same type (e.g. they are both tone features), and imagine further that i and j are both linked to X, so you have a representation like
X /\ i j
If i and j are different, then there is a contour. Now what if i and j are the same? Has there been discussion on a constraint against, as it were, "trivial contours?"
[subsequently added] Also, let's say that we want to ban the above representation, but still permit
X X | | i j
So a simple OCP rule will not suffice. Then further suppose that
X /\ i j
when i and j are different, is also permitted.
[a second addition] To narrow the problem further, let's say that three elements, i,i,j are to be linked to two nodes, X1 and X2. The two possibilities where every element is associated with some node, and every node is associated with some element are:
X1 X2 X1 X2 /\ | | /\ i i j i i j
Both of these have one OCP violation, and one violation of NoContour, so these two constraints cannot be used in combination to solve the problem.