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8 The Design Environment 233

Fig. 8.13 Step three: filtering the distribution set

Ordering,task Create Purchase Order allows one to specify a participant who will
work on the purchase order if the latter needs to be modified. So, should the task
Modify Purchase Order be executed, the participant in the net variable PO Manager
will get offered the work item.
At the second interaction point, the work item gets allocated to a participant out
of the group of participants who have been selected for this work item. Once a work
item is allocated to a specific participant, the work item offer is withdrawn from all
other participants. In the case of a user-initiated allocation, the participant who is
offered the work item can decide whether or not to accept it. On the other hand, in a
system-initiated allocation, the workflow system decides which participant the work
item should be allocated to. However, in this case the workflow designer needs to
define the appropriate allocation strategy during design time. The fourth step of the
Resource Manager Wizard provides several strategies to choose from, for example,
Round Robin or Shortest Queue (see Fig. 8.14).
At the third interaction point, the work item gets started (i.e., executed) by a
participant. This is usually done via a Web form that is linked to the manual task. The
Editor allows a designer to specify the URL of this form by clicking on Set Custom
Form... from the task’s context-menu. If no custom form is specified, a default form
is dynamically generated for the work item at runtime. If the third interaction point is
user-initiated, the participant whom the work item has been allocated to can decide
when to start the execution of that work item. In the case of a system-initiated start,
it is the workflow environment that places the work item in the participant’s started
queue.
Finally, step five of the Resource Manager Wizard allows the specification of sev-
eral participant privileges for runtime, such as suspending or skipping the execution
of a work item (see Fig. 8.15).