Dataset search in biodiversity research: Do metadata in data repositories reflect scholarly information needs?

Category—Field—Match. Per data repository and metadata standard, we computed charts that visualize which field was filled at what percentage rate and if they correspond to the categories introduced in Section “A—Information Needs in the Biodiversity Domain”. Table 7 presents a summary of all data repositories and their best matching standard. The indi- vidual results per repository and the concrete field-to-category mapping are available in our repository. Temporal expressions (TIME) and information about author and/or creator (PERSON) were mostly provided in all repositories. Apart from PANGAEA, repositories mainly provided the publication date and only partially added information about when the data was collected. Information about data type and formats was also contained in all metadata files apart from GBIF. The identified search categories were partially covered by two repositories. GBIF with EML reflects most of the categories, but fields that correspond to ENVIRONMENT, ORGAN- ISM, DATA TYPE and METHOD were rarely filled. Metadata files in PANGAEA0 s reposi- tory-developed standard Pan-MD always contained information on data parameters (QUALITY) and geographic locations. In most cases, research methods and devices used were also given. Dryad provided geographic information (LOCATION) in its dc:coverage field in at least 60%. Content analysis. Table 8 presents the five most common keywords in the metadata field dc:subject for all repositories sorted by their frequencies. The full keyword lists are avail- able in our repository.

For GBIF datasets, in 81% an empty dc:subject field was returned. Zenodo’s metadata provided keywords in 52% of the inspected cases. There are inconsistencies in how terms are entered; for example, none of the repositories seem to consider upper and lower cases. For sev- eral terms, different spellings resulted in separate entries. Numerous keywords in PANGAEA Table 7. Comparison of data repositories and their best matching standard with the information categories. The categories are sorted by the frequency of their occur- rence determined in the question analysis. The asterisk denotes the categories with an agreement less than 0.4. Environment Quality� Material Organism Process Location Data Type� Method� Anatomy� Human Intervention� Event� Time Person GBIF (EML) (3%) (11%) (35%) (8%) (18%) (publication date—100%, collection data—10%) (>90%) Dryad (OAI − DC) (60%) (publication date) (80%) PANGAEA (Pan − MD) (>90%) (100%) (100%) (Devices used— 90%, research methods —65%) (publication Date—100%, collection date—80%) (100%) Zenodo (OAI − Datacite) (100%) (publication Date) (100%) Figshare (QDC) (100%) (publication Date) (100%) Table key Orange: Unspecific (generic element), Yellow: Available (one or more elements) Amount in brackets denotes the percentage the element is filled. https://doi.org/10.1371/journal.pone.0246099.t007 PLOS ONE Dataset search in biodiversity research PLOS ONE | https://doi.org/10.1371/journal.pone.0246099 March 24, 2021 26 / 36