  This note aims to provide a systematic understanding of direct data-driven
control, enriching the existing literature not by adding another isolated
result, but rather by offering a comprehensive, versatile, and unifying
framework that sets the stage for future explorations and applications in this
domain. To this end, we formulate the nonlinear design problem from a
high-level perspective as a set of desired controlled systems and propose
systematic procedures to synthesize data-driven control algorithms that meet
the design requirements specified in the desired set. Various examples are
presented to demonstrate the comprehensiveness and adaptability of the proposed
approach.
