Sequential Relational Decomposition

The concept of decomposition in computer science and engineering is considered a fundamental component computational thinking prevalent design algorithms, software construction, hardware design, more. We propose simple natural formalization sequential decomposition, which task decomposed into two sub-tasks, with the first sub-task to be executed before second executed. These tasks are specified by means input/output relations. define study problems, decide whether given specification can sequentially decomposed. Our main result that itself difficult problem. More specifically, we problems three settings: where input explicitly, Boolean circuits, automatic show setting NP-complete, it NEXPTIME-complete, third there evidence suggest undecidable. results indicate intuitive idea as system-design approach requires further investigation. In particular, adding human loop asking for hint lowers complexity considerably.