Handling Loops in Sequence Flows

Loops are created when the flow of the Process moves from a downstream object to an upstream object. There are two types of loops that are WS-BPEL mappable: while loops and repeat loops.

A while loop has the following structure in BPMN and is mapped as shown.

A repeat loop has the following structure in BPMN and is mapped as shown.

14.2.5 Handling Data

Data Objects

BPMN Data Objects are mapped to WS-BPEL variables. The itemDefinition of the Data Object determines the XSD type of that variable.

Data Objects occur in the context of a Process or Sub-Process. For the associated WS-BPEL process or WSBPEL scope, a variable is added for each Data Object in the corresponding WS-BPEL variables sub clause, as follows:

[ D1 ]= <variable name="[D1-name]" type="[D1 -structureDefinition]"/>

Properties

BPMN properties can be contained in a Process, Activity, or an Event, here named the “container” of the property. A BPMN property is mapped to a WS-BPEL variable. Its name is derived from the name of its container and the name of the property. Note that in the case of different containers with the same name and a contained property of the same name, the mapping to WS-BPEL ensures the names of the associated WS-BPEL variables are unique. The itemDefinition of the property determines the XSD type of that variable.

A BPMN Process property is mapped to a WS-BPEL global variable. A BPMN Event property is mapped to a WSBPEL variable contained in the WS-BPEL scope representing the immediately enclosing Sub-Process of the Event (or a global variable in case the Event is an immediate child of the Process). For a BPMN Activity property, two cases are distinguished: In case of a Sub-Process, the WS-BPEL variable is contained in the WS-BPEL scope representing the Sub-Process. For all other BPMN Activity properties, the WS-BPEL variable is contained in the WS-BPEL scope representing the immediately enclosing Sub-Process of the Activity (or a global variable in case the Activity is an immediate child of the Process).

Input and Output Sets

For a Send Task and a Service Task, the single input set is mapped to a WSDL message defining the input of the associated WS-BPEL activity. The inputs map to the message parts of the WSDL message. For a Receive Task and a Service Task, the single output set is mapped to a WSDL message defining the output of the associated WS-BPEL activity. The outputs map to the message parts of the WSDL message.

The structure of the WSDL message is defined by the itemDefinitions of the data inputs of the input set.

For the data outputs of the output set, the WSDL message looks as follows.

Data Associations

In this sub clause, we assume that the input set of the Service Task has the same structure as its referenced input Message, and the output set of the Service Task has the same structure as its reference output Message. If this is not the case, assignments are needed, and the mapping is as described in the next sub clause.

Data associations to and from a Service Task are mapped as follows.

Data associations from a Receive Task are mapped as follows.

</receive>

D4

Data associations to a Send Task are mapped as follows.

Expressions

BPMN Expressions specified using XPath (e.g., a condition Expression of a Sequence Flow, or a timer cycle Expression of a Timer Intermediate Event) are used as specified in BPMN, rewriting access to BPMN context to refer to the mapped BPEL context.

The BPMN XPath functions for accessing context from the perspective of the current Process are mapped to BPEL XPath functions for context access as shown in the following table. This is possible because the arguments MUST be literal strings.

Table 14.2 – Expressions mapping to WS-BPEL