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6 Declarative Workflow 187
[Truck-Load (TL)] [Less than Truck-Load (LTL)]

Arrange Pickup Arrange Delivery
Appointment Appointment

Arrange Delivery Arrange Pickup
Appointment Appointment

Arrange Delivery Arrange Pickup
Appointment Appointment
Create Bill of
[else] Lading
[no delivery information]
Create Shipment
Infomation Document
[else: both]
Arrange Delivery
[no pickup information] [no delivery information] Appointment
Arrange Pickup Arrange Delivery
s
Appointment Appointment

(a) The truck load (TL) (b) Less than truck load (LTTL)
Fig. 6.8 Two parts of the carrier appointment YAWL subnet of the order fulfillment process

a way that task pickup must be executed before the task bill,and task delivery can
be executed either before or after the task bill. While the YAWL net for the Car-
rier Appointment subprocess explicitly specifies all possible orderings of the related
tasks, these orderings can be implicitly specified by using ConDec constraints, as
shown in Fig. 6.9a. Constraints 1..* on tasks delivery and bill specify that each of
these tasks must be executed at least once. The precedence constraint specifies that
task bill can be executed only after task pickup is executed. The automaton pre-
sented in Fig. 6.9b is generated for the mandatory formula of this model, and it
represents exactly all traces that satisfy this model. From the initial state (S 0 ), the
accepting state (S 5 ) can only be reached if bill and delivery are executed and bill is
not executed before pickup.

Example 4 (The ConDec model for the TL process (cm TL )). In the TL branch of
the process, the goal is to execute tasks pickup, delivery, and shipment in any order.