Design-based research is a relatively new methodology developed by and for educational researchers. It is interventionist - in that a purposeful change is made in a functioning educational context. It is participatory in that researchers work with practitioners. It is theoretical in that theory is used to design the intervention. Further, it generates theory through studied application in the original and subsequent educational contexts in which the innovation is used.
(From http://cider.athabascau.ca/CIDERSIGs/DesignBasedSIG/ )
Design-based research is research on how theory and innovative learning environments converge to support human learning and performance. The dual purposes of design-based research are to 1) develop theoretical design principles that are grounded in systematic inquiry about the process of teaching and learning, and 2) develop innovative tools, technologies, methods, and resources that put these design principles into practice."
(Generated by Thomas Reeves, Richard West and Chandra Orrill during EDIT 9990 online discussion)