Recommended practices for supplemental data

Since various forms of supplemental data (SD) have been introduced in academic publications, it has become necessary to establish guidelines to systematically process, indicate, and distribute such data. This material aims to help the science journals establish rational SD policies and guidelines and to ensure compliance with such policies and to manage them consistently. Generally, SD can be approached in a literal way by categorizing ‘appendices’ as ‘additional or separately added complementary materials’ and ‘supplements’ as ‘materials supplemental to the research in a comprehensive sense,’ rather than by viewing SD as an independent component of an article. The recommended practices of the National Information Standards Organization of USA advise the classification of SD into either ‘integral content’ or ‘additional content’ according to the content’s functional relationship to the associated article. If a public depository is used for SD, the author can ensure the perpetuity of data accessibility by assigning a digital object identifier. Science journals should adopt appropriate SD policies and describe them in detail in the instructions for authors to ensure consistent compliance with those policies. Additionally, they should be able to inspect and maintain links, repositories, and metadata associated with the SD for specific articles on an ongoing basis.