A portion of the Xenopus Anatomical Ontology's developmental map. Shown are the anatomical features to which the sensorial layer of the ectoderm gives rise. Types in green boxes have develops_from relationships to their parents. Also shown here are examples of the other two anatomical relationships that are integral to the XAO: ectoderm is_a primary germ layer; and the auditory ossicle, etc., are parts_of the auditory apparatus. The develops_from relationships are transitive: given that the lens develops from the lens placode and the lens placode develops from the sensorial layer, it is implied that the lens develops from the sensorial layer (and more generally from ectoderm). Transitivity operates over is_a relationships as well, e.g. the lens may be inferred to develop from a primary germ layer.