I have read various articles about incomplete contracts, like Hart's papers and Milgrom's papers.
But I have not found a paper that defines mathematically, in the most general way possible, what an contract is, and how a contract can be more, or less, "incomplete".
Is there a general model that has as special cases the incomplete contracts studied in the literature (e.g. by Hart, Incomplete Contracts and the Theory of the Firm, and others), and perhaps also as special case the complete contracts?
Note: I am not necessarily asking for a general model that can include all the reasons for incomplete contracts (thought that would be nice too). Just a model that can be used to state how (in)complete a particular contract is, whatever the reason.