Two Alternative Views on Control Design with Degree Constraint

The purpose of this note is to highlight similarities and differences between two alternative methodologies for feedback control design under constraints on the McMillan degree of the feedback system. Both sets of techniques focus on uniformly optimal designs. The first is based on the work of Gahinet and Apkarian, and Skelton, Iwasaki, Grigoriades and their co-workers, while the other is based on earlier joint work of the authors with C. I. Byrnes.