The Access to Biological Collections Data (ABCD) schema is a highly structured data exchange and access model for taxon occurrence data (specimens, observations, etc. of living organisms), i.e. primary biodiversity data.

In 2006, the schema was extended, to include an 'Extension For Geosciences', to form the ABCDEFG Schema^[1] and, in 2010, TDWG published a draft standard extension for DNA; ABCDDNA.^[2]