protocol

datalog_protocol

Datalog and incremental rule engine protocol (stratified negation subset).

Availability:
logtalk_load(datalog(loader))
Author: Paulo Moura
Version: 0:1:0
Date: 2026-02-13
Compilation flags:
static
Dependencies:
(none)
Remarks:

  • Rules: Rules are represented as rule(Id, Head, Body) where Body is a list of literals using Term for positive, neg(Term) for negative, and agg(Op, Template, Goals, Result) for aggregates where Op is one of count, sum, min, or max.

  • Facts: EDB facts are represented by callable and ground terms.

  • Limitations: Current version requires aggregate dependencies to be in lower strata.

Inherited public predicates:
(none)

Public predicates

clear/0

Clears all loaded rules, base facts, derived facts, and explanation supports.

Compilation flags:
static
Mode and number of proofs:
clear - one

load_program/1

Loads a full program represented as a list of rule(Id,Head,Body) and fact(Fact) terms, replacing current engine state.

Compilation flags:
static
Template:
load_program(Program)
Mode and number of proofs:
load_program(+list) - one

add_rule/3

Adds or replaces a rule. Rule safety is checked.

Compilation flags:
static
Template:
add_rule(Id,Head,Body)
Mode and number of proofs:
add_rule(+nonvar,+callable,+list(callable)) - one

remove_rule/1

Removes all rules matching a rule identifier.

Compilation flags:
static
Template:
remove_rule(Id)
Mode and number of proofs:
remove_rule(+nonvar) - one

begin/0

Starts a transaction by saving the current engine state snapshot.

Compilation flags:
static
Mode and number of proofs:
begin - one

commit/0

Commits a transaction by discarding the saved state snapshot.

Compilation flags:
static
Mode and number of proofs:
commit - one

rollback/0

Rolls back a transaction by restoring the saved state snapshot.

Compilation flags:
static
Mode and number of proofs:
rollback - one

assert_fact/1

Asserts a ground EDB fact if not already present.

Compilation flags:
static
Template:
assert_fact(Fact)
Mode and number of proofs:
assert_fact(+callable) - one

retract_fact/1

Retracts an EDB fact if present.

Compilation flags:
static
Template:
retract_fact(Fact)
Mode and number of proofs:
retract_fact(+callable) - one

materialize/0

Computes rule closure from current EDB facts and loaded rules using a fixpoint algorithm.

Compilation flags:
static
Mode and number of proofs:
materialize - one

update/3

Applies incremental EDB updates and propagates derivation additions/removals; returns the resulting truth delta.

Compilation flags:
static
Template:
update(Inserts,Deletes,Delta)
Mode and number of proofs:
update(+list(callable),+list(callable),-compound) - one

query/1

Enumerates currently true facts (EDB + IDB).

Compilation flags:
static
Template:
query(Goal)
Mode and number of proofs:
query(?callable) - zero_or_more

query/2

Same as query/1 while returning the unified goal as the second argument.

Compilation flags:
static
Template:
query(Goal,Bindings)
Mode and number of proofs:
query(?callable,?callable) - zero_or_more

explain/2

Returns one explanation for a currently true fact.

Compilation flags:
static
Template:
explain(Fact,Explanation)
Mode and number of proofs:
explain(+callable,-nonvar) - zero_or_more

(rules)/1

Returns the loaded rules.

Compilation flags:
static
Template:
rules Rules
Mode and number of proofs:
rules-list - one

facts/1

Returns all currently true facts as a sorted list.

Compilation flags:
static
Template:
facts(Facts)
Mode and number of proofs:
facts(-list(callable)) - one

predicate_stratum/3

Enumerates predicate strata as functor, arity, and stratum number.

Compilation flags:
static
Template:
predicate_stratum(Functor,Arity,Stratum)
Mode and number of proofs:
predicate_stratum(?atom,?integer,?integer) - zero_or_more

strata/1

Returns all strata grouped by stratum number and contained predicates.

Compilation flags:
static
Template:
strata(Strata)
Mode and number of proofs:
strata(-list) - one

Protected predicates

(none)

Private predicates

(none)

Operators

(none)