LDC-E4107 — A priority between rules that can never conflict

What it means

A priority orders two rules for the case where both could fire on the same claim. When the two rules conclude different predicates, they never compete over one claim: no reasoning path ever consults the edge between them, so the edge never applies.

The compiler warns and keeps the package green. Remove the edge, or point it at two rules that conclude the same predicate.

Example

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity A;
relation p(a: A) kind institutional;
relation q(a: A) kind institutional;
relation s(a: A) kind institutional;
rule r1 defeasible { for a: A; when p(a); then q(a); }
rule r2 defeasible { for a: A; when p(a); then s(a); }
priority e1: r1 > r2 reason demo.diagnostics.r1;

Fix

Arxo Law

language "law.core" version "0.2";
package demo.diagnostics version "0.1.0";
namespace "urn:law:demo:diagnostics";

entity A;
relation p(a: A) kind institutional;
relation q(a: A) kind institutional;
relation s(a: A) kind institutional;
rule r1 defeasible { for a: A; when p(a); then q(a); }
rule r2 defeasible { for a: A; when p(a); then s(a); }

Engine message

The engine reports this in its own wording:

Output

example.law:11:10: warning LDC-E4107: priority between provably non-conflicting rules "r1" (q) and "r2" (s) — heads over different predicates (§192)

Related

• Priority — how competing rules are ordered.