A PGraph is a directed graph: each link connects exactly two nodes, establishing one as the "from" node and the other as the "to" node. This direction establishes the order in which the nodes' patterns are expected in the input stream. The order starts with the start node.
The PGraph is user-defined. Nodes are created by double-clicking the left mouse button on the drawing surface at the position desired for the new node. Links between nodes can be created once two or more nodes have been created. See the node and link topics for more information.