Hi Vasia! There is no fundamental reason, we simply have not gotten around to implementing it, yet. Any help along these lines is highly welcome.
One reason that held us back is that we need to make sure that the key of the solution set and the key of the join is the same. That is hard to verify with general functions. One approach is to actually change the delta iteration API to define the keys only at one place (the definition of the iteration), and offer special "joinWithSolution" and "coGroupWithSolution" functions, rather then using the regular join syntax (which allows to create invalid constructs). What are your thoughts on this, from a DeltaIteration user perspective? Greetings, Stephan
