Connectors

Purpose: As its name suggests, the job of the connector is to connect model elements. The software provides for two distinct types of connector: the action connector and the information connector. Action connectors are signified by a solid, directed wire. Information connectors are signified by a dashed wire. To select an info connector, click and hold the connector icon on the palette. Then select the info connector from the drop-down list that will appear.

Legal connector linkages are illustrated in Figure 4-24. As the diagram suggests, the software will not let you connect either an info or action connector directly into a stock. The only way to change the magnitude of a stock is through a flow.

Figure 4-24
Legal Connector Linkages

Selection and Placement:

Select the connector icon by clicking once on the icon in the Building Block palette. To obtain the info connector, select the dashed arrow icon from the drop down list.
Slide the cursor (the point of the arrow) to the place where the connector will start. This starting place must be within the boundary of a stock, flow regulator, converter, or decision process diamond on your screen.
Click-and-hold. Drag the cursor to the target converter, flow regulator, or decision process diamond. When you make contact, the target will turn gray. Release your click.

Note on Circular Connections: In drawing connector linkages, you may encounter an alert which tells you that circular connections are not allowed. Mechanically, this alert means that you have attempted to create a chain of converters and/or flows, such that one converter or flow ultimately depends upon itself. The software can not resolve the resultant simultaneous equations. To resolve the simultaneity, you must include a stock somewhere in the chain. The Introduction to Systems Thinking Guide provides a conceptual discussion of circular connections.

Surface Operations: Figure 4-25 details surface operations that may be performed on a connector.

Figure 4-25
Connector Surface Operations

Dialog Operations: Because the connector tool is used to indicate connections, it has no associated define dialog. The interrelationships between model variables are specified in the converter, flow, and stock building blocks.