Taxonomy (biology) new common (or apomorphic) traits. However, certain phenetic methods, such as neighbor joining, have found their way into cladistics, as a reasonable approximation of phylogeny when more advanced methods (such as Bayesian inference) are too computationally expensive. Modern taxonomy uses database technologies to search and catalogue classifications and their documentation. While there is no commonly used database, there are comprehensive databases such as the "Catalogue of Life", which attempts to list every documented species. The catalogue listed 1.64 million species for all kingdoms as of April 2016, claiming coverage of more than three quarters of the estimated species known to
Structure (category theory) the morphisms are group homomorphisms: that is, of structures on one type, and mappings respecting that structure. Starting with a category "C" given abstractly, the challenge is to infer what structure it is on the objects that the morphisms 'preserve'. The term "structure" was much used in connection with the Bourbaki group's approach. There is even a definition. Structure must definitely include topological space as well as the standard abstract algebra notions. Structure in this sense is probably commensurate with the idea of concrete category that can be presented in a definite way — the topological case means that infinitary