Gremlin
GraphTraversal
One of the core concepts of tinkerpop/gremlin is the GraphTraversal It's interface has a generic definition as:
public interface GraphTraversal<S,E> extends Traversal<S,E>
and at https://markorodriguez.com/ the Author Marko Rodriguez explains the ideas behind using an generic approach vor handling Graphs. The Java implementation is available on github.
S is generic Start class, and E is a generic End class as explained in the Apache Tinkerpop documentation.
For example let's assume we want to Traverse the family tree of a person.