Core commands and aggregations of such commands are provided to programmers to enable them to generate programs that can be parallel-processed without requiring the programmer to be aware of parallel-processing techniques. The core commands and aggregations abstract mechanisms that can be executed in parallel, enabling the programmer to focus on higher-level concepts. The core commands provided include commands for applying a function in parallel and distributing and joining data in parallel. The output of each core command can implement an interface that can enable underlying mechanisms to stitch together multiple core commands in a cohesive manner to perform more complex actions.