Node, Port and Link Logic

To ensure a robust codegen compilation, we have set several rules and logics for nodes, ports and links.

Node Logic

• A node is a Xircuits component.
• Each canvas will have a Start and Finish node, which cannot be deleted.
• Nodes can be locked. Nodes that are locked cannot be moved nor deleted.
• All component library nodes must be linked to compile and execute a workflow.

Port Logic

• Each node will have ▶ Ports and optionally parameter ports.
• Parameter Ports are inArg and outArg rendered into inPorts and outPorts respectively.
• You can only link from an outPort to an inPort.

Flow [ ▶ ] Ports

• Flow Ports indicates sequence of execution.
• All flow ports must be linked from Start to Finish.
• You cannot create a flow loop.
• You can only link flow ports to flow ports, and parameter to parameter ports.

Compulsory Ports

• Compulsory inPorts are rendered inCompArg indicated with the * symbol.
• A parameter must be supplied to compile and run the workflow.

Port Type Checking

• A port may have a specific type it is expecting, eg str or int. Supplying a wrong type will throw out an error tooltip.

• An exception to this rule is the any port, which will bypass any port type check.

• The following table is the port visualization of certain data types. Those not included in the list will simply have the port blank.

  Data Type	Port UI
  string	" "
  int	1
  float	1.0
  boolean	⊤⊥
  list	[ ]
  tuple	( )
  dict	{ }
  any	[_]

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Link Logic

• A link is created when you select and drag from a port.
• Linking an outPort to an inPort will indicate data passing between components.
• If a link is not dropped on a port, it will prompt the component tray interface. Selecting one of the components will automatically link the ▶ ports.
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Smart Link

• When linking ▶ ports, Xircuits will perform a check whether the parameter port labels have an intersection, and if so, attempt to link it.
  • Example: The out_sparksession wil be linked to the in_sparksession as there is a sparksession intersection.
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Stacking Links

• For string, list and dict ports, you are able to stack multiple links. For each additional link, the values will be concatenated (if strings) or added (if list or dict).