PDI sources provide example implementations of transformation steps. Each PDI core step is located in a sub-package of
org.pentaho.di.trans.steps found in the engine/src folder. The corresponding dialog class in located in
org.pentaho.di.ui.trans.steps found in the ui/src folder.
For example, these are the classes that make up the Row Generator step.
dialog classes of the core PDI steps are located in a different package and source folder. They are also assembled into a separate jar file. This allows PDI to load the UI-related jar file when launching Spoon and avoid loading the UI-related jar when it is not needed.