"The goal of the Physics Instructional Resource Association (PIRA) Demonstration Classification Scheme is to create a logically organized and universally inclusive taxonomy giving a unique code to every lecture demonstration. (...) The topic and concept divisions of the structure loosely follow the standard textbook organization of chapter and section, although they were created to organize existing demonstrations, not cover the entirety of introductory physics, and therefore skip some areas of the curriculum covered by standard textbooks. As the standard curriculum changes over the years, categories have been created to contain the many demonstrations rendered obsolete by modern texts. Single concept films, videos, and computer programs are sometimes included but such resources have not been systematically identified."