alter_table(:classification_rlshp) do
      add_foreign_key([:resource_id], :resource, :key => :id)
      add_foreign_key([:accession_id], :accession, :key => :id)
      add_foreign_key([:classification_id], :classification, :key => :id)
      add_foreign_key([:classification_term_id], :classification_term, :key => :id)