[DBXREFS]

[DBXREFS]
  ;   KEY = [ EXTERNAL_DB_ID NAME ACCESSION_REGEX DISPLAY_NAME_REGEX ]
  GO = [ 1000 GO /^goslim_goa:GO:(.+)/ ]
  INTERNAL = [ 9999 Internal /^Internal:(.+)/ /^Internal:(.+)/ ]
  REFSEQ_MRNA = [ 1801 RefSeq_mRNA /^Genbank:(NM_.+)/ ]
  REFSEQ_MRNA_PRED = [ 1806 RefSeq_mRNA_predicted /^Genbank:(XM_.+)/ ]
  REFSEQ_PEPTIDE = [ 1810 RefSeq_peptide /^Genbank:(NP_.+)/ ]
  REFSEQ_PEPTIDE_PRED = [ 1815 RefSeq_peptide_predicted /^Genbank:(XP_.+)/ ]
  REFSEQ_RNA = [ 1820 RefSeq_rna /^Genbank:(NR_.+)/ ]
  REFSEQ_RNA_PRED = [ 1825 RefSeq_rna_predicted /^Genbank:(XR_.+)/ ]
  ENTREZGENE = [ 1300 EntrezGene /^GeneID:(.+)/ ]
  UNIPROT = [ 2250 UniProtKB_all /^UniProtKB:(.+)/ ]

Pattern matching to associate Dbxref attributes in the GFF with the correct database. For each Dbxref in the .gff file, the value array contains the Ensembl external_db_id, the display_name for the external_db and regular expressions to extract the database accession and display name from any additional information in the string.