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13 The Business Process Modeling Notation 361
Table 13.1 Mapping data from BPMN to YAWL
BPMN YAWL
Property Variable
Process property reference Process variable reference
<process name>.<property name> <process decomposition name>/
<variable name>
Task property reference Task variable reference
<process name>.<task name>.<property name> <task decomposition name>/
<variable name>
Assignment (Assigntime = Start) Input parameter
Assignment (Assigntime = End) Output parameter
Condition (ConditionType = Expression) Predicate
Condition (ConditionType = Default) Last predicate is “true()”
Property visible in embedded subprocess Variable of composite task
Property visible in independent subprocess Variable of composite task

variable’s type. This principle applies whether the property is defined at the level of
a process model or at the level of an individual task. For example, properties track-
points, currentTrackpoint,and trackpointNoticesdefined at the top of Fig. 13.4 are
defined at the level of the process model. They will therefore be mapped into vari-
ables attached to the corresponding YAWL net. Meanwhile, in the same figure, three
properties (trackpoints, trackpointNotice,and skipTrackpoint) are defined under the
task Issue Trackpoint Notice. These properties are mapped to variables defined at the
level of the corresponding YAWL task. A subtle difference here is that, in YAWL,
variables defined at the level of a task are grouped inside a decomposition, while in
BPMN, properties are assigned directly to a task. Therefore, a decomposition needs
to be defined under task Issue Trackpoint Notice and the above three variables must
be attached to this decomposition.
BPMN assignments that are executed when a task starts (i.e. that have “Assign-
time = Start”) assign values from a process property to a task property. Such
assignments map to YAWL input parameters. The from part of the assignment is
an XQuery expression that refers to properties of the process, and the to part is a
reference to a property of the task. In the from and the to parts, references to BPMN
properties must be mapped to references to YAWL variables. Assignments that are
executed when a task completes (i.e., that have “Assigntime = End”) assign values
from a task property to a process property. Such assignments map to YAWL output
parameters in a similar manner. For example, Fig. 13.4 contains two assignments
attached to task Issue Trackpoint Notice.The AssignTime of the first assignment is
Start. Accordingly, this assignment is mapped into an input parameter in the corre-
sponding YAWL task decomposition. This input parameter copies the value of the
net variable trackpoints into the task variable with the same name. Meanwhile, the
AssignTime of the second assignment is End. Hence, this assignment is mapped into
an output parameter in YAWL.
A BPMN condition on a sequence flow is mapped to a YAWL predicate on a flow.
There are two possible cases: either the condition is represented as an (XQuery)