Formal analysis remains outside the mainstream of system design practice. Interactive methods and tools are regarded by some to be on the margin of useful research in this area. Although it may seem relatively academic to some, it is vital that this the so-called “theorem proving approach” continue to be as vigorously explored as approaches favoring highly automated reasoning. Design derivation, a term for design formalisms based on transformations and equivalence, represents just a small twig on the theorem-proving branch of formal system analysis. A perspective on current trends is presented from this remote outpost, including a review of the author’s work since the early 1980s.