For a system of tasks that may lock resources, the “wait-for” one of these constructs can be used to represent the system state and identify deadlocks. Weisfeiler-Leman algorithms are used on these objects, which may be used to construct a static schedule by building one of these objects. In 2015, László Babai announced work on a problem named for these objects that runs in quasipolynomial (15[1])time. The expression D minus A gives a type of (*) Laplacian representing these objects. One of these objects that obeys the triangle inequality is used as input for the Christofides algorithm. Kruskal’s algorithm constructs a minimum spanning tree on these (10[1])objects, which may be used for causality diagramming in their directed acyclic (10[1])form. For 10 points, name these objects that consist of a collection of vertices connected by edges. ■END■