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2 The Language: Rationale and Fundamentals 41
task instances
X: X:
A A
D: 1 D: 1 D: D:
2 2
3 X:X: 3 X:X:
A A
X: X:
A A
(a) (b)

Fig. 2.11 Data interaction with multiple instance tasks

Table 2.4 External data interaction patterns
Pattern Initiator Data source Data target
Data interaction – Process Process Process Environment
to environment –
Push-oriented
Data interaction – Process Environment Process
Environment to process –
Pull-oriented
Data interaction – Environment Environment Process
Environment to process –
Push-oriented
Data interaction – Process Environment Process Environment
to environment –
Pull-oriented

element. Similar to the factors associated with passing the data elements to the
task instances, there is also the consideration of how to pass them to subsequent
tasks. In the former scenario, the data elements are coalesced and the compos-
ite data element is passed on; in the latter, a specific instance is selected for
subsequent usage.
Data Interaction between Cases denotes the communication of a data element
from one case to another. Typically this is based on communication between a
task instance in one case and a target task instance in another, although other
approaches are possible.
There are four external data interaction patterns describing scenarios for data trans-
fer between a process instance and the operating environment. These are identified
in Table 2.4. These patterns are differentiated on the basis of two factors: the
initiating party of the data interaction and the direction of the data transfer.
Although the data interaction patterns describe the passing of data elements at a
macro level, the data transfer patterns focus on the specific details associated with
the trafficking of a data element across the interface of the process component that
is receiving or emitting it.