Process Data

Process data can be stored in Variables. Variables are currently created on the process level within the Automation of the Property panel or directly from within the UserTask Editor. The specification of a Process Variable is serialized into BPMN.

The serialization of Process Variables in PROCEED is not yet BPMN conform. There is no itemDefinition, dataObject or ioSpecification created at design time and this elements are also not considered during execution of the process at runtime.

Variables are serializes as follows:


...
<process id="_09abb321-f819-480a-9827-66264d17b4df" name="PROCEED Main Process" processType="Private" isExecutable="true">
 
  <extensionElements>
      <proceed:variables>
          <!--
          name: required, unique
          dataType: required, one of: string, number, boolean, object, array, null
          description: optional, free text
          requiredAtInstanceStartup: optional, boolean, default false
          defaultValue: optional, set at design time
          enum: optional, array of strings seperated by semicolon, the value must be one of these
          const: optional, boolean, default false, non-changeable value after set for the first time
 
          dataType similar to JSON Schema: https://datatracker.ietf.org/doc/html/draft-bhutton-json-schema-validation-00#section-6.1.1
          - string: "Text" -> optional: textFormat="email|url" (default: not present, means: no string contraints)
          - number: "Number"
          - boolean: "On/Off"
          - object: "Combined Structure" -> no defaultValue and no enum in UI yet
          - array: "List" -> no defaultValue and no enum in UI yet
          -->
 
          <proceed:variable name="Maschinen Typ" dataType="string" textFormat="url" description="Gibt den Typ einer Maschine an" requiredAtInstanceStartup="true" defaultValue="https://machine-type.de/3d-printer" enum="https://machine-type.de/3d-printer;https://machine-type.de/cnc;https://machine-type.de/grinder" const="false" />
 
 
      </proceed:variables>
  </extensionElements>
  ...

A process variable is accessible within the process level and all of its sub-processes or tasks.

During execution, Activities/Tasks usually first write into local Task variables. After finishing the Tasks, the Engine writes the local variable states into the global variable states of the process instance. (Exception: Script Tasks have a function to directly change the state of a global variable.) If two Activities/Tasks write in parallel to the same global variable, the latest executions wins and overrides the global variable value.

This behaviour is a little bit different with a running call activity, because it is started as a completely separated process. Therefore, the current process variables are copied into the call activity execution at its start. After its execution, all changed or new variables from the call activity process are copied into the parent process. So, this maybe overrides a process variable at the end of the execution.

Advanced: Moreover, within PROCEED it can happen that parts of the process are executed on another Machine. When two parts are merged on one Machine, newer variables changes override older values.