Prolog indeed seems eminently suitable for this use case. For example, let us consider the first use case shown on the page: graql>> match $x isa

Prolog indeed seems eminently suitable for this use case. For example, let us consider the first use case shown on the page: graql>> match $x isa movie; $y isa person; $z isa movie value "Avatar"; ($x, $y) isa directorship; ($y, $z) isa directorship; select $x; This finds movies directed by the director of Avatar. Here are a few relations in Prolog that we can use for this example: movie('Avatar'). movie('Titanic'). movie('Aliens'). movie('Terminator 2: Judgement Day'). person('James Cameron'). directorship(X, Y) :- movie_director(X, Y). directorship(X, Y) :- movie_director(Y, X). movie_director('Avatar', 'James Cameron'). movie_director('Titanic', 'James Cameron'). movie_director('Aliens', 'James Cameron'). movie_director('Terminator 2: Judgement Day', 'James Cameron'). These are Prolog facts and rules that suffice to illustrate this use case. In Prolog, we can query this database as follows: ?- findall(X, (movie(X), person(Y), movie(Z), Z = 'Avatar', directorship(X, Y), directorship(Y, Z)), Xs). Note how closely this query corresponds to the initial example! Prolog answers with: Xs = ['Avatar', 'Titanic', 'Aliens', 'Terminator 2: Judgement Day']. Note that this is in fact more complete than what the example shows: results>> [ {"isa": "movie", "value": "Titanic"}, {"isa": "movie", "value": "Aliens"}, {"isa": "movie", "value": "Terminator 2: Judgement Day"} ] Interestingly, this misses Avatar!