The DELTA format (DEscription Language for TAxonomy) is a flexible method for encoding taxonomic descriptions for computer processing. DELTA-format data can be used to produce natural-language descriptions, conventional or interactive keys, cladistic or phenetic classifications, and information-retrieval systems.
Interactive keys differ from printed, dichotomous keys in that there is no predetermined path that the user must follow to effect identification. Interactive keys allow the flexibility of viewing characters in different orders and of selecting them in a sequence that suits the information available to the user. The characters can be presented in the ‘natural’ order, i.e. grouped together by feature, e.g. all leaf characters together, or by ‘best’ order, in which characters with the best power to separate the taxa in the group are presented first.
Both these arrangements are interchangeable within the identification process and changing from one mode to another does not affect the previous choices
