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8 The Design Environment 231
(cf. Fig. A.6 in Appendix A). The designer needs to define a Multiple Instance Vari-
able that will contain the data to be distributed to the various task instances at
runtime. The content of this variable can be taken from net variables using input
parameters. The data contained in this variable can be separated with the Splitter
query to pass a unique value to each instance task. The Accessor query can be
used to manipulate the content of the variable before the unique values are split
out (e.g., if some format conversions are needed). Upon completion of all instances,
the Instance query can be used to transform the returned XML document from each
instance to a form suitable for the Aggregate query to generate an overall result.
A Result Net Variable needs also to be specified to contain the overall result. This
variable can then be mapped onto net variables via output parameters.
Finally, data aspects also concern the timer task. This task in fact allows designers
to late-bind its expiry value to a period of time or fixed date via the use of a variable
of type YTimerType. In this way, the expiry value will be dynamically determined at
runtime.

8.4 Assigning Human Resources to the Process

The Editor provides a Resource Manager Wizard, which allows designers to assign
participants to manual tasks. This wizard can be invoked by clicking on Manage
Resourcing... from the task’s context-menu after participants have been created
in the YAWL workflow environment (see Chap. 10), the task has been assigned a
decomposition, and the task has been associated with the default worklist (i.e., the
Resource Service). It need to be ensured that the Resource Service is running so
that resources can be associated with a task. The status of the Resource Service is
reflected by the second right icon in the bottom left corner of Editor (see Fig. 8.2).
If the Resource Service is active but the status icon states this service offline, a
connection can be manually established by invoking the dialogue Resource Service
Connection Settings via menu entry Tools.
The first step of the wizard allows designers to set up the way a manual task
should be offered, allocated, and started. These are called interaction points. The
interaction points for task Create Purchase Order are shown in Fig. 8.11. At the
first interaction point, the work item gets offered to one or more participants.
The offering can be set up as system-initiated or user-initiated. In the case of a
system-initiated offering, it is required to specify the group of participants at design
time. This can be done in the second and third steps of the wizard.
Step two enables a workflow designer to select individual participants by their
name, for example, Peter Clemenza, and/or participants of a certain role, for exam-
ple, PO Manager (see Fig. 8.12).
In step three, it is possible to restrict the group of participants to those who belong
to a certain organizational group or positions or have appropriate capabilities (see
Fig. 8.13).