Extension to correlated observables

[FFroehlich]

Which problem would you like to address? Please describe.
Mapping of phospho-peptides to protein phospho sites can be ambiguous, leading to correlations in the measured data. This could be captured in the noise model, but PEtab currently doesn't allow the specification of such relationships.

Describe the solution you would like
Extend the PEtab to allow the specification of correlation groups. Specific format would have to be discussed.

Describe alternatives you have considered
Alternative is probably summation of observables to avoid errors from unaccounted correlations.