This page is under construction and subject to significant revision.

Options for Publishing Taxonomic Hierarchies

The Darwin Core taxon terms provide several options for publishing taxonomic classifications or hierarchies.

1. Parent taxa may be referenced by the literal name ("Mollusca") or by identifier reference (1234). 2. Taxonomic hierarchy can be represented in a denormalised fashion, like a typical spreadsheet where a higher taxon group is repeated for each record, or a normalized form where each taxon is referenced only once.

Examples for each are listed here. Note that the full Darwin Core taxon class includes additional terms for infraspecific taxa and higher taxon ranks not included in these examples:

Denormalised by taxon name (commonly used). In this example a row represents a distinct terminal taxon (a species in this case). Higher taxa are organised into columns. The advantage of this format is that it is easy to read. The disadvantages include repeated references to the same higher taxon, increasing the possibilities of errors and the inability to provide additional information (publication, distribution, descriptive) about the higher taxa.

Normalised by taxon reference (commonly used) This format is also referred to as a "parent-child relationship" or an "adjacency list." In this case each higher taxon is referenced only once per data row. This allows all taxa to be referenced by ID and for additional information about each taxon to be published. A taxon parent is referenced by it's identifier. The top of the hierarchy has no parent (or equal to 0). In this format a higher taxon must be included as a row in the published data.

Normalised by taxon name (rarely used). This example is the same as above but the higher taxon is referenced by literal name instead of by the ID. There are few advantages to this format. The disadvantage is that the relationship between two rows is made by matching name strings instead of name IDs. This can be problematic if there are homonyms in the data or a misspelling occurs between the two instances of the names.