A dominating set is a set of vertices of a graph such that every vertex in the graph is either in the set or a neighbor of one of the members of the set. While you can look at the material through the perspectives of the stories, activities and exercises separately, there are tutorials, which bring these things together, and take you through the material from the easiest concepts right up to the open problems. The fundamental problem in knot theory is deciding whether two knots are the same. We'll take a look at how mathematicians define what a knot is and what they mean when they say that two knots are the same, and different ways to construct a knot. The terms in the tutorials are linked to the illustrated glossary, which contains definitions of the concepts introduced.
Numbers come in to the node from the left, one from the bottom and one from the top.
When there is only one number in the node, it stops and waits for another number. When there is two numbers in the node, the node compares the numbers and send them out the right, sending the larger number to the top and the lower number to the bottom. You can get to these through the gallery, or by completing the tutorials. Note that this graph is planar. It has no crossed edges.