Operation:
Think of a Queue as a line of items awaiting entry into some process or activity (e.g., grocery store checkout line, airport ticket counter line).
Queues are FIFO (first in - first out) in their operation. Stuff enters the queue, and remains in line, waiting 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. See Chapter 14 for inflow prioritization schemes.
Modeling Dialog Operations: The Queue's Modeling Dialog is easy
to define, as shown in Figure 4-34.
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Figure 4-34 |
Outflow Dialog Operations: Multiple Queue outflows are allowed-all
must be Uniflows.
The Queue "wants" to flow everything through its outflows. As such, its flows are constrained only when there is an Inflow limited and/or Capacity constrained Conveyor, or an Oven, immediately downstream.
Unit conversion is possible in flows that connect Queues to other stocks. Unit conversion works as illustrated in Figure 4-17.
When multiple outflows are drawn from a Queue, it is possible to designate one or more of the outflows as "overflow" in their dialogs. When a higher-priority flow is blocked because of capacity constraints, the flow will be routed through the overflow. A sample overflow designation is shown in Figure 4-35.
Chapter 14 discusses the prioritization scheme employed by the software when there are multiple outflows from a Queue.
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Figure 4-35 |