Top-down design, stepwise refinement, decomposition. One of essential aspects of structured programming methods. Yes, this pertains to both software engineering and systems engineering.
Stepwise Refinement. This technique was presented in the 1971 classical paper of Niklaus Wirth (Program Development by Stepwise Refinement, CACM, 14-4)
Algorithm- Divide and Conquer.. but in terms of technique---> I think Herbert answer is good, no need to get fancy.. Just divide into small classes and methods and that will do.
About Service Oriented Arch.. bears a heavy load of network traffic and unless it has to be using such approaches are undesirable.