More ideally, I think that the whole DFT instruction file should be provided inside of the CIF.
(...)
Of course the software name and the version should be given. This would allow for some reproducibility test and for example test files. The fact that cell parameters are optimized or not (and other details) will appear there.
The entire instruction file is something which in Saulius' scheme is at level 2. It is definitely the ideal situation if every entry would have all information up to level 2. But while for some codes that will be straightforward (one input file and go), for others it would require many input files and a sequence of commands (with varying options) to go from the initial structure to the optimized one in a reproducible way (and as codes evolve, the input might quickly get incompatible). Strictly requiring that all this information is present, would scare away many entries that would nevertheless have been useful.
Providing different levels is an elegant solution. The question then is: what is the strictly necessary information that must be provided (= level 0)? Items that have been suggested so far for level 0 are:
*cif of the final structure *publication reference *level of theory (XC within DFT, or name of method if not DFT) *full optimization or only positions
Part of this information will be repeated in the full input files if level 2 is included, but that is not a problem.
Stefaan