Graphs come with a set of common terms. To begin with, a graph is made up of a set of things, hereafter referred to as nodes and a set of connections between nodes , know as arcs .
Graph - A set of nodes, with a set of arcs connecting the nodes. While graphs have a wider applicability, graph here is synonymous with process definition.
Also know as: Process Definition, Network, Workflow
Node - An element of a graph. A node corresponds roughly to an action as defined previously. Nodes can be thought of as pieces of code, waiting to be executed when their turn comes.
Also known as: Vertex, Place
Arc - A directed connection between two nodes. Directed means that arcs have a start node and an end node. In some cases, an arc may have a label, or name.
Also know as: Edge, Transition
Predecessor - If two nodes are connected by an arc then the node at the beginning of the arc is the predecessor of the node at the end of the arc. How nodes are connected by arcs defines the order of execution. Generally a node may not execute until at least one, potentially many or all, of its predecessors have executed. Nodes may have many arcs exiting and entering them.
These definitions cover the parts of a process definition. However, they don't cover how that process definition is actually executed. When a process definition gets executed, the execution is called a process . Somehow, a process must track which nodes are being executed. This is generally accomplished by placing markers called token on the active nodes.
Process - An executing process definition. A process definition may have have zero, one or many processes executing at any given time.
Also known as: Case, Instance, Workflow
Token - The set of active tokens marks the current process state. Tokens generally point to a node which is currently executing. Tokens sometimes have associated state, which is a way of passing data from node to node.
Also know as: Execution