How to create facts in prolog?

You can create facts a prolog file and load them using consult function.

For example,

animals.pl

bigger(elephant, tiger).
bigger(tiger, rabbit).
bigger(rabbit, sparrow).
bigger(sparrow, ant).

1 ?- consult(animals).
true.

2 ?- bigger(tiger, rabbit).
true.

3 ?- bigger(dragon, bluewhale).
false.

You can also use assert function to define facts in prolog terminal.

1 ?- assert(bigger(elephant, rabbit)).
true.

2 ?- assert(bigger(rabbit, ant)).
true.

3 ?- bigger(elephant, rabbit).
true.

assert(bigger(elephant, rabbit)).

assert(bigger(rabbit, ant)).

Above two statements define the facts.

bigger(elephant, rabbit).

Above statement asks prolog, is elephant bigger than rabbit?

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