Article category definitions Article Category Definition Primary theory A primary theory article develops a seminal theory that is not an extension of another. It is original work that suggests a concept that is entirely new to the field. Secondary theory A secondary theory article builds off of a primary theory, but suggests new direction for research. Model A model article develops a descriptive representation that can be used to characterize a system. Measurement A measurement article collects data (either qualitative or quantitative) and draws conclusions directly from that data. Review A review article draws conclusions from numerous sources to develop new conclusions and areas for further work.