A relation between continuant instances c1 and c2 where within a protocol application, measurement of c1 is related to a what would be the measurement of c2. (another definition)

is_proxy_for

position on a gel is_proxy_for mass and charge of molecule in an western blot. Florescent intensity is_proxy_for amount of protein labeled with GFP. Examples: A260/A280 (of a DNA sample) is_proxy_for DNA-purity. NMR Sample scan is a proxy for sample quality. Within the assay mentioned here: https://wiki.cbil.upenn.edu/obiwiki/index.php/Chromium_Release_assay level of radioactivity is_proxy_for level of toxicity

http://purl.obolibrary.org/obo/IAO_0000123

Alan Ruttenberg