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2 The Language: Rationale and Fundamentals 81

Fig. 2.39 Allocation strategies for work distribution

Shortest queue allocation: This ﬁlter ensures that any work items associated with
a task are only routed to a single user where the user is selected from the group
of potential users on the basis of which of them has the shortest work queue.
In YAWL this means that the selected user has the least number of incomplete
work items in their worklist. In the event that two user have the same number of
incomplete work items, one of them is selected at random.
Figure 2.39 illustrates the conﬁguration of allocation strategies in YAWL. It is only
possible to conﬁgure these strategies for tasks that are allocated by the system, that
is, in the screen shown in Fig. 2.36 where the interaction strategy is speciﬁed for
a task, and the second option must be set such that the allocation is done by the
system.

Advanced User Operating Modes

YAWL supports two advanced operating modes for user interaction with the system.
These modes are intended to expedite the throughput of work by imposing a deﬁned
protocol on the way in which the user interacts with the system and work items are
allocated to them. These modes are described below.

Chained execution: Chained execution is essentially an operating mode that a
given user can choose to enable. Once they do this, upon the completion of a
given work item in a process, should any of the immediately following tasks in
the process instance have potential to be routed to the same user (or to a group
of users that include the user), then these routing directives are overridden and

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