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6 Declarative Workflow 197

c: Shipment Planner + SSU (shortest queue) c: Shipment Planner + SSU (time round robin)
Prepare Route Estimate Trailer Carrier
Guide Usage Timeout
Order preparation
1..* took too long
delivery
1..* 1..*
pickup shipment
s: SupplyOfficer + SUS - suspension/ Prepare
resumption, stateful-reallocation Transportation Quote
[Truck-Load (TL)] [Single Package (SP)]
[Less than Truck-Load (LTL)]
Less thanTruck-
Truck-Load l
Load

1..* Arrange Pickup s: Supply Officer +
Modify Pickup Modify Delivery Appointment historical (the person who
c: Warehouse Officer delivery has done the most)
Appointment Appointment
1..*
precedence
pickup bill
Arrange Delivery s: Supply Officer (retain
Appointment familiar)
Modify Delivery Modify Pickup
s: Supply Officer c: Warehouse Officer
Appointment Appointment
Create Carrier s: Supply Officer – capability:
Manifest Bachelor in SC & L Mgt
Produce
Shipment Notice c: Warehouse Admin Officer
the freight is physically picked up
Fig. 6.17 Combining YAWL and declarative workflows
Table 6.3 Various types of flexibility and support of constraint-based workflows
Flexibility Support
Flexibility by design Model verification
Flexibility by underspecification Monitoring instance states
Flexibility by change Ensuring correct instance execution
Flexibility by deviation Ensuring correct instance completion
Monitoring states of constraints

parent-workflow, or by allowing for late specification (at runtime). Third, dynamic
change of instances of ConDec models, which is described in Sect. 6.4, allows for
flexibility by change. Fourth, the existence of optional constraints in ConDec models
allows for flexibility by deviation.
Apart from being flexible, declarative workflows should and can support users in
several ways. Constraint models can contain an arbitrary number of constraints that
interfere in subtle ways, which can cause errors in models. Verification of constraint