Direct-sink vertex

As an illustration, consider the sequencing graph of Figure 8.6, where a number in a vertex represents its execution delay/or a particular input sequence. Shaded vertices denote direct-sink vertices. The completion of execution of all direct-sink vertices results in the completion of the execution of the entire graph. Note that if the source vertex is direct-sink for a particular input sequence, then by definition the sequencing graph is stateless for that input sequence. 

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