Methods and systems facilitating a programmer to program parts of a program in data flow programming to produce directed acyclic graphs (“DAGs”), and then merge the graphs at runtime for efficiency and scalability. Large merged DAG can typically be processed with greater efficiency than the collection of smaller DAGs. As a result, smaller DAGs may be created while the execution of the program realizes the increased efficiency of executing a larger DAG based on the merging of the smaller DAGs. In accordance with methods and systems consistent with the present invention, a programmer creates individual data flow directed acyclic graphs in a program.