4.14.2 The recorded database

recorda(+Key, +Term, -Reference)

Assert Term in the recorded database under key Key. Key is a small integer (range min_tagged_integer ...max_tagged_integer, atom or compound term. If the key is a compound term, only the name and arity define the key. Reference is unified with an opaque handle to the record (see erase/1).

recorda(+Key, +Term)

Equivalent to recorda(Key, Term, _).

recordz(+Key, +Term, -Reference)

Equivalent to recorda/3, but puts the Term at the tail of the terms recorded under Key.

recordz(+Key, +Term)

Equivalent to recordz(Key, Term, _).

recorded(?Key, ?Value, ?Reference)

True if Value is recorded under Key and has the given database Reference. If Reference is given, this predicate is semi-deterministic. Otherwise, it must be considered non-deterministic. If neither Reference nor Key is given, the triples are generated as in the code snippet below.^{88Note that, without a given Key, some implementations return triples in the order defined by recorda/2 and recordz/2.} See also current_key/1.

        current_key(Key),
        recorded(Key, Value, Reference)

recorded(+Key, -Value)

Equivalent to recorded(Key, Value, _).

erase(+Reference)

Erase a record or clause from the database. Reference is a db-reference returned by recorda/3, recordz/3 or recorded/3, clause/3, assert/2, asserta/2 or assertz/2. Fail silently if the referenced object no longer exists. Notably, if multiple threads attempt to erase the same clause one will succeed and the others will fail.

instance(+Reference, -Term)

Unify Term with the referenced clause or database record. Unit clauses are represented as Head :- true.