Subgraphs with no edge connected to SubgraphInput component do not declare any input ports, therefore cannot receive input data so will likely be used as Readers .
Figure 46.1. Subgraph - Reader
Subgraphs with no edge connected to SubgraphOutput component provide no output ports, therefore cannot produce any data so will likely be used as Writers .
Figure 46.2. Subgraph - Writer
Subgraph having connected both components ( SubgraphInput and SubgraphOutput ) is essentially a Transformer .
Figure 46.3. Subgraph - Transformer
Subgraphs with no edge connected to SubgraphInput or SubgraphOutput components can be used as utility Executors . As they cannot be connected to other components in parent graph the execution of subgraphs without ports is controlled via Phases .
Figure 46.4. Subgraph - Executor