I have looked a bit at code examples of Airflow, but was worried that it seems to have a similar problem as a lot of other pipeline tools: That in the main workflow specification, dependencies are specified between tasks only, not between the individual inputs and outputs of each task (between tasks rather than data).

This means that this info needs to be implemented "manually" in some less declarative manner somewhere else, breaking the declarative-ness of the workflow specification.

I have posted about it some time ago here, mentioning AirFlow specifically: http://bionics.it/posts/workflows-dataflow-not-task-deps