The intent of the Exclusive Pattern is to branch from a single activity to exactly one of several paths, based on the evaluation of a condition. This pattern is known as a XOR-split.
The need for such a pattern is big and this is used widely in everyday’s activity. To understand the power of the XOR split we just give an example of a bank customer who wants to login to the i-bank. The customer gives the password and if the password is correct he is redirected to a welcome page. Otherwise if something goes wrong the customer is informed that he cannot access his account. So this behavior is modeled as an XOR split from Get approval to send welcome user page or Send rejection message. The effect is that of an if statement in the process.
Implementations of this widely supported pattern include control constructs (this can be a switch statement in BPEL and BPML) and explicit split elements(such as XOR gateway in BPMN and the diamond in UML activity diagrams).
Simple merge
The intent of a simple merge pattern is that several exclusive conditional paths converge on a single activity, which starts executing when the one chosen path completes. The pattern is also known as XOR-Join. A simple merge is actually the endpoint – XOR join- of a process that splits and which started by an exclusive choice. In programming we can assume that it is the end of an if statement . now in languages in which conditional processing is modeled as a control structure (such as BPEL and BPMN) the control structure can manage the merge(for example, when the switch case in BPEL completes, its selected case is quaranteed to have completed.)
Giannis Giataganas IS Consultant, BPM Analyst Bsc in Informatics, AUEB MscIS, Athens University of Economic and Business
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