According to Sumner and Dawe (2001), there are several major categories of modification:
- Composition is creating a new resoource by combining existing resources. Cobbling together a course from different topical units, diagrams and syllabi or putting together lists of resource links for additional reading would be examples.
- Factoring creates several resources out of one larger resource by breaking it down into simpler parts that can more easily shared. Imagine taking a "whole course" resource and splitting it into small chunks: syllabus, topical units, homeworks sets, exams, diagrams, tables, etc.
- Refining is the process of modifying or adding to an existing resource without significantly changing its fundamental nature. When an existing resource is overly specific to a particular time, place or person, stripping out this information is necessary but doesn't change the content of the resource.
- Abstraction refers to identifying commonalities across a number of resources and creating a new resource around these commonalities.