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2 The Language: Rationale and Fundamentals 71

... has accessor query ... / ...

... has splitter query .../ ...
MI Task MIParameter

... has instance query .../...

... has aggregator query … / ...

XQuery
... has input .../... Expression
SimpleParameter
... has output .../...
Var Parameter
Task
(id)
.../belongs to... .../... has source ...
... belongs to .../...
Net or Task .../... has target ...
(id) ... is of .../... (XML Schema)
DataType

Name
... has ... /...
Net
.../contains ...
Flow
BoolExpr
(XPath)
... precedes .../... ... has ... / ...
Fig. 2.32 Object role model: YAWL data perspective

2.6 Resources

YAWL provides support for a broad range of work distribution facilities, inspired by
the Resource Patterns that have not been previously embodied in other PAISs. Tra-
ditional approaches to work item routing based on itemization of specific users and
roles are augmented with a sophisticated array of new features. There are a variety
of differing ways in which work items may be distributed to users. Typically these
requirements are specified on a task-by-task basis and have two main components:
1. The interaction strategy by which the work item will be communicated to the
user, their commitment to executing it will be established and the time of its
commencement will be determined.
2. The routing strategy, which determines the range of potential users that can
undertake the work item.