# Implicit Connectors

This section identifies the implicit connections generated by the software between different stock/flow configurations. Implicit connections are important because they can limit your ability to create explicit connections between model variables. If an implicit connection exists between model variable "A" and model variable "B," the software will prevent you from drawing a connector from variable "B" back to variable "A" in most cases. Instead, you'll get a message that circular connections are not allowed, and a notification of the implicit connection which is at the root of the problem. As noted on page 14-3, in a few cases the software will override its implicit rules to allow connections between variables.

Implicit connections exist with:

- Non-negative Reservoirs

- Queues

- Conveyors

- Ovens

- Sub-models

Figures 14-1 and 14-2 identify these implicit connections (shown in red), and briefly describe their implications.

Figure 14-1 Implicit Connectors: Reservoirs, Queues, Conveyors

Figure 14-2 Implicit Connectors: Ovens, Sub-models

###### Situations in which the software overides its implicit connection rules

In some cases, the implicit connection rules shown in Figures 14-1 and 14-2 could lead to circular connections. To prevent this from happening, the software will systematically "break" implicit connections in order to prevent circular connections. In all cases, the software still maintains the dependency relationships that you have made with explicit connectors.

Figure 14-3 shows the most common instances in which such "breaking" occurs. The figure also notes the run-time implications of the breaking. Run-time implications will appear only when non-negativity constraints come into play.

Figure 14-3 Instances where Implicit Connectors are Broken