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within the work item thus far (stateful reallocation), or to reset the work item data
to its original values (stateless reallocation).
Further, at runtime, a participant with the necessary privileges may choose to pile
a task, so that all future instances of work items of the task across all current and
future cases of the process are directly allocated to the participant, overriding any
design time resourcing specifications; and/or chain a case, which means that for all
future work items in the same process instance where the distribution set specified
includes the participant as a member, each of those work items is to be automatically
allocated to the participant and started.
Finally, an administrator has access to a Worklisted queue, which includes all
of the currently active work items of all participants, whether offered, allocated,
started, or suspended, from which a task can be manually reoffered, reallocated, or
restarted to another participant.

10.3 Organizational Model

Before work items can be assigned to (human) resources, a data source that describes
those resources must first be established. That is, at a minimum, the Resource Ser-
vice needs access to data that details the attributes of a set of human resources and
the relationships (if any) between them. Then, a list of such resource descriptors can
be provided to the Editor, from which particular resources may be chosen at design
time, for each task in a process specification, to potentially perform the execution of
work items derived from those tasks at runtime.
In the Resource Service, a human resource is referred to as a participant, that is,
someone who willingly participates in the performance of tasks within a workflow
instance, progressing it towards completion. Although a set of discrete participants
is all that is required to allocate work items to resources, more typically a partici-
pant is a member of some kind of organization, and therefore is defined in various
ways within an organizational model. An organizational model describes the rela-
tionships between the participants of an organization, and their jobs, roles, duties,
managerial hierarchies (lines-of-reporting), and so on. The Resource Service pro-
vides a default organizational model database and tools to administrate it. On the
other hand, organizations with existing organizational data sources (such as other
RMDSs, LDAP, text files, XML, and so on) may use that data directly instead, by
importing it through an interface provided by the service and mapping the data into
the model (see Sect. 10.4 for details).

10.3.1 The YAWL Organizational Model

The Resource Service defines a typical, generic organizational model into which
participants and their various relationships may be placed. The service’s organiza-
tional model is an implementation of the ORM diagram shown in Chap. 2, Fig. 2.33.