o APUPA is a concept developed by the father of Library Science, Shiyali Ramamrita Ranganathan, to define the natural and hierarchical relationship of materials in a bibliographic classification scheme.
o APUPA stands for Alien-Penumbral-Umbral-Penumbral-Alien.
o Umbral represents the exact information source matching the subject area. The Penumbral sources are closely related. The Alien sources are unrelated.
o APUPA explains how a classification scheme’s linear structure creates meaning for the user by bringing together closely related subject areas. A user naturally views the most relevant information source (Umbral) first, then moves either left or right to related resources (Penumbral), and then to unrelated resources (Alien).
o APUPA patterns are dynamic. Any book or other resource within a classification scheme can be an Umbral source and any resource can also be Penumbral or Alien, depending on the subject.
o If you are seeking a book on growing roses, that book is your Umbral source. Books about pruning roses, which is a related topic but not exactly the same, are Penumbral sources. Books about composting would be Alien, or unrelated sources.