Understanding the codes

A letter coding system has been adopted in preference to a fully numerical coding system or an alpha-numeric system (as used in the NVC and EUNIS systems). This has a number of advantages. It enables the construction of intuitive codes which can readily be related to their respective types without recourse to the full type title. Furthermore, it enables changes to the order in which the types are presented without the need to change a numerically sequenced code. This was particularly useful in the early development phase of the classification, but has continued to be of use during subsequent revisions of the classification.

Construction of codes follows a few simple rules, which achieve consistency throughout the classification whilst aiming to keep the resultant codes relatively short and intuitive. Familiarity with the rules for code construction and with the types themselves, by those working regularly with the classification, results in rapid use of codes as a short-hand means of referring to the types defined.

Codes are defined for each level in the classification. Within a level, they comprise one or several elements. They are based on the following rules:

1. Broad habitat and main habitat codes are based on habitat factors or gross biological features (e.g. macrophytes and biogenic reefs).

2. Biotope complex, biotope and sub-biotope codes are based wherever possible upon the most characteristic taxa (which preferably also dominate spatially/numerically) (preferably no more than two per biotope complex, biotope or sub-biotope).

3. Where the biological composition is too complex to derive a simple code, features of the habitat are used (e.g. VS for variable salinity).

4. Codes for habitat factors, higher taxa and descriptive community features (e.g. park, crustose) are derived from a standard lexicon. A full list of codes used is contained in the hierarchical list which can be downloaded from the classification website.

5. Codes for names of genera are derived using the first three letters of a genus or higher taxon name (e.g. Ala for Alaria, Chr for Chrysophyceae). Codes for species names are derived using the first letter of the genus and the first three letters of the specific name (e.g. Ldig for Laminaria digitata).

6. Within the code each new element of the code starts with a capital letter.

7. As far as practical the code elements are unique, but some duplication is adopted in the interests of keeping codes short. The code for any given type (i.e. for the level defined, regardless of whether it is stringed with higher codes – see below) is always unique.

8. All the biotope/sub-biotope codes are unique, so users familiar with the classification can refer to individual biotopes using only the codes for these levels in the hierarchy.

9. The full codes are compiled using the code for each level in the hierarchy, separated from the next level by a full stop, starting with the broad habitat (level 2), followed by the main habitat, biotope complex and so on. For example LS.LSA.MoSa.AmSco.Eur:

2	broad habitat	littoral sediment	LS
3	main habitat	littoral sand	LSA
4	biotope complex	mobile sand	MoSa
5	Biotope	Amphipods and Scolelepis spp.	AmSco
6	Sub-biotope	Eurydice sub-biotope	Eur

NOTE: to avoid confusion, others using the classification should not erect similar codes for types not currently described in the national classification.