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Triggers & Transfer Objects

These tools do not belong to any target system: They are available in every flow, regardless of which plug-ins are configured.

They are not the only ones: Most triggers and transfer objects are provided by the plug-ins—the database trigger is part of the database plug-in, and MQTT Subscribe is part of the MQTT plug-in. These target-system-specific triggers are listed under their respective plug-ins in the Plug-ins chapter; “Which Trigger When” explains which trigger is appropriate in which situation.

A trigger starts a flow. It fires either on a schedule—at a fixed time or cyclically—value-based, when a monitored value changes, or event-based, when a connected system sends a message. A flow will not start without a trigger.

A transfer object is a processing step within the flow: it reads data, writes it, transforms it, or branches the flow.

You can drag both from the tool palette on the right side of the window onto the configuration area and connect them there using Item Links, which you drag between the entries of two transfer objects. Details on each step can be found under “Configure Flow.”

The sections in this chapter​

  • Triggers – start a flow: the Cron trigger at scheduled times via a Cron expression, the Time trigger cyclically, either with a start delay or starting at an absolute time, and the Variable trigger when a variable changes.
  • Variables – global and local variables, secrets, and aggregation metrics, along with transfer objects for reading and writing.
  • Subprocesses – the common concept of outsourced flows: contract, scope variables, publication, runtime and call status, plus conditions (IF), error handling (Try/Catch), functions (FX), and the Change Gate, which only passes values when they change.
  • Data Formats (ETL)—read, generate, and validate JSON, XML/XPath, and CSV.
  • Custom Code (.NET C# Script)—create custom transfer objects and triggers as C# scripts using the low-code principle.
  • Helper Objects – operate within a flow: Text Replace inserts placeholders with data types, formats, and cultures into a text; the Calculator performs calculations using placeholders, formulas, and rounding; the Note documents a flow without providing or recording any data itself.