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Why should you use this? In case of working with biological data there is always dispute about the naming of the observed species. PESI is the European name list which has a reference to all species descriptions. If you are looking for a description of species as a metadata within a project you could use this service to give correct descriptions. This is metadata on the level of records, not data sets.
PESI is the back bone of the INSPIRE metadata vocabularies concerning biological data.