"CDAO stands for "Comparative Data Analysis Ontology", a formalization of concepts and relations relevant to evolutionary comparative analysis, such as phylogenetic trees, OTUs (operational taxonomic units) and compared characters (including molecular characters as well as other types). CDAO is being developed by scientists in biology, evolution, and computer science. In general, ontologies are designed to support formal or automated reasoning. Our aim in developing CDAO is to provide the language support for representing, and reasoning over, phylogenetic data and metadata. When CDAO is fully developed and supported by software, it will be possible for one researcher to represent information with conceptual richness, and for another research (or a computer) to access that same conceptual richness. The current version of CDAO is a kind of free-floating ontology not linked into an "upper" ontology. The reason for this is that, when we first began to develop CDAO, we did not understand where the concepts and relations would fit in terms of available upper ontologies. We're still not entirely sure."