Type-Directed Diffing of Structured Data, Victor Cacciari Miraldo, Pierre-Évariste Dagand, Wouter Swierstra. A datatype-generic representation for tree diffs, motivated specifically by syntax tree diffing. The authors note the mismatch between the notion of a minimal _tree diff and a usable tree diff, in human terms, and thus discuss tree alignments rather than edits. Further, they make use of nondeterminism to produce the set of possible alignments rather than selecting a single one (since they haven’t yet formalized a metric for usability that would guide a decision procedure).