rify

Rify is a forward chaininginference engine designed specifically for use on in-memory RDF graphs.

It accepts conjunctive rules with limited expressiveness so reasoning is bounded by O(n^k) in both memory and in computation where n is the number of nodes in the input RDF dataset.

Given premises and target statement[s], rify can generate a proof which can be used to quickly verify the result programatically.

Logical rules are defined as if-then clauses. Something like this:

structRule{if_all:Vec<[Entity;4]>,then:Vec<[Entity;4]>,}// Notice it's `[Entity; 4]`, not `[Entity; 3]`. This reasoner operates on Rdf Quads, not triples.// You can still reason over triples by binding a unique resource e.g. `RdfTerm::DefaultGraph`// as the graph in all rules and all quads.enumEntity{/// A a named variable with an unknown value.Unbound(String),/// A literal with a constant value.Bound(RdfTerm),}// actual definitions of these types are templated but this is the gist// You get to define this type! Here is an example definition.enumRdfTerm{Blank(usize),Iri(String),Literal{datatype:String,value:String,lang_tag:Option<String>,},DefaultGraph,}

Rify doesn't care whether its input and output is valid rdf. For example, it will happily accept a quad whose predicate is a literal. https://www.w3.org/TR/rdf11-concepts/#section-triples

Use

Three functions are central to this library: prove, validate, and infer.

prove

use rify::{
prove,Entity::{Unbound,Bound},Rule,RuleApplication,};// (?a, is, awesome) ∧ (?a, score, ?s) -> (?a score, awesome)let awesome_score_axiom = Rule::create(vec![// if someone is awesome[Unbound("a"),Bound("is"),Bound("awesome"),Bound("default_graph")],// and they have some score[Unbound("a"),Bound("score"),Unbound("s"),Bound("default_graph")],],vec![// then they must have an awesome score[Unbound("a"),Bound("score"),Bound("awesome"),Bound("default_graph")]],).expect("invalid rule");assert_eq!(
prove::<&str,&str>(// list of already known facts (premises)&[["you","score","unspecified","default_graph"],["you","is","awesome","default_graph"]],// the thing we want to prove&[["you","score","awesome","default_graph"]],// ordered list of logical rules&[awesome_score_axiom]),Ok(vec![// the desired statement is proven by instantiating the `awesome_score_axiom`// (you is awesome) ∧ (you score unspecified) -> (you score awesome)RuleApplication{
rule_index:0,
instantiations: vec!["you","unspecified"]}]));

validate

use rify::{
prove, validate,Valid,Rule,RuleApplication,Entity::{Bound,Unbound}};// same as abovelet awesome_score_axiom = Rule::create(vec![[Unbound("a"),Bound("is"),Bound("awesome"),Bound("default_graph")],[Unbound("a"),Bound("score"),Unbound("s"),Bound("default_graph")],],vec![[Unbound("a"),Bound("score"),Bound("awesome"),Bound("default_graph")]],).expect("invalid rule");let proof = vec![// (you is awesome) ∧ (you score unspecified) -> (you score awesome)RuleApplication{
rule_index:0,
instantiations: vec!["you","unspecified"]}];letValid{ assumed, implied } = validate::<&str,&str>(&[awesome_score_axiom],&proof,).expect("invalid proof");// Now we know that under the given rules, if all quads in `assumed` are true, then all// quads in `implied` are also true.

infer

use rify::{infer,Entity::{Unbound,Bound},Rule};// (?a, is, awesome) ∧ (?a, score, ?s) -> (?a score, awesome)let awesome_score_axiom = Rule::create(vec![// if someone is awesome[Unbound("a"),Bound("is"),Bound("awesome"),Bound("default_graph")],// and they have some score[Unbound("a"),Bound("score"),Unbound("s"),Bound("default_graph")],],vec![// then they must have an awesome score[Unbound("a"),Bound("score"),Bound("awesome"),Bound("default_graph")]],).expect("invalid rule");letmut facts = vec![["you","score","unspecified","default_graph"],["you","is","awesome","default_graph"]];let new_facts = infer::<&str,&str>(&facts,&[awesome_score_axiom]);
facts.extend(new_facts);assert_eq!(&facts,&[["you","score","unspecified","default_graph"],["you","is","awesome","default_graph"],["you","score","awesome","default_graph"],],);

Recipes

In addition to normal cargo commands like cargo test and cargo check the ./justfile defines some scripts which can be useful during development. For example, just js-test will test the javascript bindings to this library. See ./justfile for more.

License

This project is licensed under either of Apache License, Version 2.0 or MIT license, at your option.