Stocks

The default type of stock is the reservoir. Think of a reservoir as a pool of water, or as an undifferentiated pile of "stuff." A reservoir passively accumulates its inflows, minus its outflows. Any units that flow into a reservoir will lose their individual identity. Reservoirs mix together all units into an undifferentiated mass as they accumulate.

The reservoir stock type is represented by a simple rectangle. In this documentation, the term "stock" refers to reservoir-type stock.

Think of a conveyor as a moving sidewalk or a conveyor belt. Material gets on the conveyor, rides for a period of time, and then gets off. For example, you might use a conveyor to represent students in school or work process in a factory.

• The transit time for a conveyor can be either a constant or a variable.
• The operation of the conveyor can be arrested.
• Multiple inflows to a conveyor are allowed (uniflows only).
• Both capacity and inflow limit can constrain entry to a conveyor.
• Multiple leakage flows are allowed. For more information on conveyor outflows, see To create leakage flows for conveyors.

Think of a queue as a line of items awaiting entry into some process or activity (for example, a grocery store checkout line or an airport ticket counter line).

• Queues are FIFO (first in, first out) in their operation. Stuff enters the queue and remains in line, waiting for its turn to exit the queue.
• Multiple inflows are allowed (uniflows only). The contents of each inflow are given their own slot or element in the queue.
• The queue exerts no behind-the-scenes control over its inflows. Any control from a queue to its inflows must be explicitly represented in the inflow logic.
• The software prioritizes multiple inflows into a queue. For more information, see Flow prioritization.
• Multiple outflows are allowed (uniflows only). For more information on queue outflows, see To define queue outflows.

Note: When defining an equation for the queue, you can use the SIZE builtin to report the queue's length.

Think of an oven as a processor of discrete batches of stuff. The oven opens its doors, fills (either to capacity or until it is time to close the door), bakes its contents for a time (as defined by its outflow logic), and then unloads them in an instant. For example, a bank teller is an oven. The bank teller helps one customer at a time with transactions, then moves to the next customer.

• The operation of an oven can be arrested.
• Only a single uniflow can flow into an oven.
• The inflow to an oven can come from a cloud, a reservoir, or a queue.