The editorial in the current issue of Cell outlines new guidelines for supplemental materials for Cell Press publications. The contention is that, although supplements are a unique and "powerful advantage of online publishing", they have become dumping sites,
Unfortunately over the years supplemental material has evolved into a seemingly limitless repository for additional “stuff”: a wide range of control experiments, preliminary next-step experiments, data responding to specific reviewers concerns, results that just “don’t fit” within the main paper, extended discussions,and methodological details. It has become a mechanism for expanding the overall content of a paper without any delineated change in editorial standards.
In designing the new framework for supplements, the editorial board is imposing "conceptual" limits, as opposed to rigorous length limits. They designate three major "conceptual categories" for supplemental material:
- data that "provides deeper support for the points made in the main paper"
- large data sets and multimedia
- methodological detail
I will be interested to see how this works out. It sounds logical and reasonable and straightforward. In many high-impact factor journals, it is frustrating and sometimes even difficult to follow what the authors have done. My personal opinion is that the main paper should be able to stand on its own. I shouldn't need a 20-page supplement to believe the paper. That's what dissertations are for ;)