Subgraphs with no edge connected to the SubgraphInput component do not declare any input ports, therefore cannot receive input data so will likely be used as Readers.

Subgraphs with no edge connected to the SubgraphOutput component provide no output ports, therefore cannot produce any data so will likely be used as Writers.

Subgraph having connected both components (SubgraphInput and SubgraphOutput) is essentially a Transformer.

Subgraphs with no edge connected to the SubgraphInput or SubgraphOutput components can be used as utility Executors. As they cannot be connected to other components in a parent graph, the execution of subgraphs without ports is controlled via Phases.