Sorry, my wording was incorrect. I should not have used the word impossible, thank you for the resources you have provided, my point was more that with the standard gui, it makes things easier in a pick up and play way but any sustained time using an application, the tradeoff between being what people describe as "easy to use" and being extensible and streamable becomes very useful.
There is a GUI programming paradigm, called Stream Processors. One of earlier Haskell GUI libraries was developed over those processors.
Take a look at Fudgets: http://www.altocumulus.org/Fudgets/
You can pipe them, you can arrange them into DAGs and trees (as in DirectShow or Gstreamer). You can create cyclic structures.
I haven't seen Intents. But I think that Stream Processors are closer to (and even surpass) command line pipelining.