Table 2.

Top ten features for each backend ranked by the Gini importance.

Backend	Most important features (descending)
CLP(FD)	Function application, max conjunct depth, forward compositions, relational overrides, nested logic with conj., nested logic with implications, equalities, function variables, subset ratio, identifier count
Kodkod	Function application, function vars, forward compositions, set op., nested logic with conj., nested logic with disj., nested logic with impl., avg. powerset nesting, identifier count, relational overrides
Z3	Relational operators, domain ops, functions, function vars, avg. powerset nesting, domain restrictions, unbounded domains, identifier count, max. conjunct depth, function application