Inter-relationships of pronephric kidney tissues and structures, their developmental timing, and curated data. A. The developmental timing of a Xenopus anatomical entity (blue fill) is asserted by starts_during and ends_during relationships to specific embryonic stages (green fill), demonstrated here by the 'pronephric kidney’(yellow fill). B. Ontological assertions about developmental timing place constraints on data curation. Expression of the gene slc12a1 in a NF stage 37/38 embryo (assayed by fluorescent in situ hybridization; XB-IMG-2158) is evident in 'early distal tubule’. C. Expression of slc5a1.2 in a NF stage 37/38 embryo (assayed via in situ hybridization; XB-IMG-2348) is recorded by curators as taking place in the 'early proximal tubule’ and 'late proximal tubule’. Intermediate NF stages have been omitted for simplicity. Relationship types (colored arrows): is_a (black), part_of (blue), develops_from (purple), starts_during (green), ends_during (red), preceded_by (orange). Images (B) by P. Vize, and (C) by Zhou & Vize , used with permission, ©Elsevier (2004).