Create CDNO annotation documentation

[kaiiam]

We should create some documentation that explains how users should use CDNO for data annotation. We need to emphasize that the material component and chemical concentration hierarchies seem similar but are different and that people should use the latter for data annotation.

[LilyAndres]

Hey @kaiiam sounds good, how do we start?

[kaiiam]

Sorry for the slow response, a first start would be just to draft up some material in a google doc or wiki page. Not currently my top priority. The other thing to consider is that there are a variety of vocab systems which could be used for food component annotation. CDNO gives really specific semantics for chemical concentrations but various data sources exist which might give outputs as CHEBI terms, smiles, inchikeys etc. Having guidance or even better, mappings between systems would maybe help to make various food composition data more interoperable. For generic targeted food composition CDNO would work nicely, but for untargeted analyses, (e.g., lipid omics or proteomics) data might be represented or just map-able to an inchikey or similar. CDNO manually keeping up with that might get unfeasible as more untargeted methods are used for food analyses. I think these are important questions to raise with the USDA led Minimum Food Composition data standard working group, whenever that gets a chance to take off.