Assignment allocates responsibility, behavior performance, storage, or execution. Its direction is active element to behavior, behavior to passive element, and active element to passive element; the older bidirectional notation is deprecated but still allowed. Separate assignments of several active elements to one behavior mean either can perform all of it, so when all are needed use grouping, a junction, or a collaboration.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.