Compute the left or right trace of an endorelation.
relation_trace(x, which)
an endorelation.
one of "left" or "right", or a unique
abbreviation thereof.
Let \(R\) be a crisp endorelation. The left and right trace of \(R\) contain all pairs \(x, y\) for which \(z R x\) implies \(z R y\) for all \(z\) (left trace) or \(y R z\) implies \(x R z\) for all \(z\) (right trace), respectively. These are the largest (in the natural ordering of relations with the same domain) relations such that \(R * S \le R\) or \(S * R \le R\), respectively (where \(*\) denotes composition). In the fuzzy case, the memberships of the traces can be defined as the infima over the corresponding fuzzy membership implications. See Chapter 2.3 in Fodor+Roubens:1994 for more information.
Fodor+Roubens:1994