I am more and more hooked on the idea of using message-driven finite-state-transducers as a mathematical model to describe #DDDesign Aggregates. This would enable automated determinism proofs, unions, concatenation, projections, and any other operation that is available for FSMs.
A transducer is defined as a sextuple: (finite input alphabet / commands, finite output alphabet / events, initial state, finite set of states, state transition function (state, command) -> state / behaviours, output function (state, command) -> event). #DDDesign
I spent a bit of time implementing a very naive UserRegistration Aggregate based on an also naive generic transducer in #Scala, you can check ou gist.github.com/tPl0ch/5c6c9a0…
It felt very natural to design it that way. Static types can already provide the input, state & output sets.
It felt very natural to design it that way. Static types can already provide the input, state & output sets.
There are related patterns like the State Pattern, but none gives us the mathematical soundness that a proven model gives us. I will talk about this idea and much more in tomorrow's @virtualDDD meetup on #DDDesign Aggregates!
