Is there a data structure to represent changes to a DAG over time, with fast reproduction of instances of the DAG? - Computer Science Stack Exchange
https://cs.stackexchange.com/questions/136879/is-there-a-data-structure-to-represent-changes-to-a-dag-over-time-with-fast-repPersistent data structure - Wikipedia
https://en.wikipedia.org/wiki/Persistent_data_structurescala - Immutable data structure for a DAG? - Stack Overflow
https://stackoverflow.com/questions/48254821/immutable-data-structure-for-a-dag