Summary: We investigate analogies between the methodologies typical of the dynamics of polymeric liquids and those used in a seemingly entirely unrelated area, viz. granular flow theory, and we show that the essential conceptual content of the approach is in fact the same in both areas. We also discuss the theory of compressible flow of granular materials, for which an analogy with the dynamics of polymeric liquids is not available, but which is an area where similarities and crucial differences with classical compressible flow theory are of interest.