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12.3.16 CentralBufferNode


   A central buffer node is an object node for managing flows from multiple sources and destinations.


   • ObjectNode (from BasicActivities , CompleteActivities ) on page 408


   A central buffer node accepts tokens from upstream object nodes and passes them along to downstream object nodes. They act as a buffer for multiple in flows and out flows from other object nodes. They do not connect directly to actions.


   No additional attributes


   No additional associations


   See semantics at ObjectNode. All object nodes have buffer functionality, but central buffers differ in that they are not tied to an action as pins are, or to an activity as activity parameter nodes are. See example below.


Issue 8233 -put in correct figure references

   See notation at ObjectNode. A central buffer may also have the keyword «centralBuffer» as shown below. This is useful when it needs to be distinguished from the standalone notation for pins shown on at the top of Figure 12.120 and Figure

    12.127 .


   Figure 12.68 - Optional central buffer notation


   In the example below, the behaviors for making parts at two factories produce finished parts. The central buffer node collects the parts, and behaviors after it in the flow use them as needed. All the parts that are not used will be packed as spares, and vice versa, because each token can only be drawn from the object node by one outgoing edge. The choice in this example is non-deterministic.

   Part Part

Figure 12.69 - Central buffer node example




   Central buffer nodes give additional support for queuing and competition between flowing objects.

*Changes from previous UML

   CentralBufferNode is new in UML 2.0.