You can use Composable's Fluent API to author and run dataflows in code. No GUI required. Composable's platform is open and completely extensible in sense that anyone can add applications or first class modules to the system, including swapping out some of the more internal components.
Pipes are probably the original instantiation of dataflow processing (dating back to the 1960s). I gave a tech talk on some of the frameworks:
https://www.youtube.com/watch?v=3oaelUXh7sE
Composable Analytics is a similar solution, but users create the apps using a dataflow methodology (sexy apps). Allows for much more flexibility because you can change the guts of the data processing. It's also very performant because parts of the app can be parallelized.
I think businesses still need flexible / easy to use systems that allow end-users to create solutions quickly. This may involve analysts, IT professionals, and devs working together on the same platform. For examaple, an IT pro writes the sql queries, an analyst writes the regression algorithms, and the devs writes the output adapters.
Typically, by the time you get the dev team to fully implement the solution, it has missed its mark and the analysts have moved on.
Players in the mashup landscape are "trying" to provide scalable and robust, yet flexible and easy-to-use systems.
plug - flowreports.co is one of these ... and it can be self-hosted.