In this paper, we introduce a new way to categorise existing educational research making it possible to find new previously overlooked research topics. This novel categorisation system is based on the didactic foci of the research papers. Our categorisation scheme is not data driven as in previously published categorisation systems but is derived from the didactic triangle, which is a theoretical model describing the elements of a teaching-studying-learning processes.

The didactic-focus-based categorisation system can be used to promote discussion about missing types of research foci within the computing education research (CER) community. In addition, the new categorisation system supports meta-level analysis of published research papers and thus contributes to the discussion of the goals and the present state of CER. We analyse previously existing categorisation systems and describe how our system differs. Finally, we give two examples how to apply the new theoretical categorisation system. First, we use research papers published in ICER conferences 2005-2009 as our source material to illustrate how to apply the new theoretical categorisation system for revealing a number of areas for novel research such that seem to have received little attention from the CER community. The second example highlights how the categorisation system can be used to find overlooked research topics on some specific research area (in our example students' success in CS1).