Towards interoperable research site documentation - Recommendations for information models and data provision.

Information related to research sites is essential when describing the context of observations. It is a key element of site-based research infrastructures (RIs) and their catalogues. This paper is dedicated to the comparison of (meta)data models describing research sites in the ecosystem domain. A special focus is on sites in terrestrial and freshwater ecosystems. This should provide the basis for a common site-based data model to exchange data from different site-based catalogue services. This should substantially improve interoperability of site-level information between different RIs. For this purpose, we selected well-established site catalogues that feature web accessible documentation of the sites and means to export this information. Using either dedicated descriptions of the data models, or, if these were not available, by deriving the data model from the records extracted from the catalogues, we identified the commonalities, differences and gaps of the underlying data models. Based on the findings, we define a set of mandatory core fields to be used in every site catalogue in the ecosystem domain. A set of additional fields are recommended to be implemented. In addition, we formulate general recommendations on how to best serve site data, considering the technical interface, the data format and the data license. The aim of these recommendations is to increase interoperability between site catalogues in general and the selected catalogues in particular. This fosters analyses of the existing ecosystem research infrastructures on a national, regional and global scale and increase the ability of these infrastructures to answer large-scale environmental questions.