Skip to content


Repository files navigation

Structured Descriptive Data

  • Download: Download
  • Status: TDWG current (2005) standard
  • Category: Technical specification
  • Permanent URL:
  • TDWG task group: Biological Descriptions Interest Group
  • Date submitted: 2006-11-24
  • Date published: 2005-09-16
  • Last modified: 2007-05-08


In taxonomy, descriptive data takes a number of very different forms.

Natural-language descriptions are semi-structured, semi-formalised descriptions of a taxon (or occasionally of an individual specimen). They may be simple, short and written in plain language (if used for a popular field guide), or long, highly formal and using specialised terminology when used in a taxonomic monograph or other treatment.

Dichotomous keys are specialised identification tools comprising fragments of descriptive data arranged in couplets forming a branching tree. Each fragment (lead) comprises a small (occasionally verbose) natural-language description.

Raw data descriptions usually comprise repeated measurements of parts of individual specimens, and are the basis from which the more abstracted descriptions in natural language and coded descriptions are derived. Few taxonomists consistently record and archive their raw data in a standardised format.

The goal of the SDD standard is to allow capture, transport, caching and archiving of descriptive data in all the forms shown above, using a platform- and application-independent, international standard. Such a standard is crucial to enabling lossless porting of data between existing and future software platforms including identification, data-mining and analysis tools, and federated databases.

See also the SDD Primer.

Preferred citation

Hagedorn G., Thiele K., Morris R. & Heidorn, P.B. 2005. Structured Descriptive Data (SDD) w3c-xml-schema, Version 1.0. Biodiversity Information Standards (TDWG)