The set of DIA operations is grouped into four types:
- Source operations create DIAs from outside data, they have no parent DIAs and thus initiate the data-flow graph.
- Local operations require no communication and are composed with the previous operations.
- Distributed operations are the main class and contain many parameterized transformations which have one or more DIAs as inputs and result in one DIA as output.
- Actions are terminal nodes in the data-flow graph which trigger computation of a result and deliver this back to the user program.
1.8.13 
