Label Modifiers are State Connections that connect a source node to a target label (L) of a resource connection or a state connection. It indicates how state changes of the source node (dS) modify the value of the target label as indicated by the modifier's label (M). The new value takes effect on the subsequent time step. Thus, the next value of label that is the target of a number (n) of label modifiers is given by the following formula:
L(t+1) = L(t) + Sum(M*dS)
For example, in figure below every resource added to pool A adds 2 to value of the resource flow between pools B and C. Thus the first time B is activated, 1 resource flows to A and 3 resources flow to C, the second time, 1 resource still flows to A, but now 5 resources flow to C. The label of a label modifier always starts with a plus or minus symbol indicating incrementation or decrementation.
Label modifiers are frequently used to model different aspects of game behavior. For example, a pool might be used to represent a player's accumulated property in a game of Monopoly. The more property a player has, the more likely it is that player will collect money from other players. This can be represented by the diagram in figure below. (Note that many details are omitted in this diagram, in particular the diagram does not show how a player might acquire property.)