 Since around 1970, "D"-module theory has been built up, mainly as a response to the ideas of Mikio Sato on algebraic analysis, and expanding on the work of Sato and Joseph Bernstein on the Bernstein–Sato polynomial.Early major results were the Kashiwara constructibility theorem and Kashiwara index theorem of Masaki Kashiwara.The methods of "D"-module theory have always been drawn from sheaf theory and other techniques with inspiration from the work of Alexander Grothendieck in algebraic geometry.