Piecewise linear aggregation functions based on triangulation

We introduce a method to construct piecewise linear binary aggregation functions on the unit interval, based on a triangulation of the unit square with one additional vertex. We derive conditions under which such piecewise linear aggregation functions possess additional interesting properties, such as idempotence, symmetry, Lipschitz continuity and 2-monotonicity. This construction method can also be used to approximate binary aggregation functions. In this way, copulas and quasi-copulas are approximated by singular copulas.