Crate asdi

Another Simplistic Datalog Implementation (in Rust).

This package provides a data model to represent Datalog programs in memory, a parser for the textual representation, and some evaluation implementations.

The text representation parser is a separate feature, so if you only need to construct and evaluate programs using the API you may opt out of the Pest parser and support.

Status

1. Library API mostly stable, but minimal, will try and make the construction API more ergonomic.
2. Library Documentation good top-level documentation but very little else right now.
3. Library validation checking basic checking, but some is done in the parser and needs to be in the library.
4. Parser full support for the core language as well as pragmas, require more unit tests.
5. I/O relations are now connected to the file input/output pragmas, the io module includes traits for reading/writing relations as well as basic JSON and CSV support.
6. Evaluation current evaluator is basically top-down brute force and does not support any additional language features.

Example

parent(xerces, brooke).
parent(brooke, damocles).

ancestor(X, Y) ⟵ parent(X, Y).
ancestor(X, Y) ⟵ parent(X, Z) ⋀ parent(Z, Y).

?- ancestor(xerces, X).

use asdi::edb::{Attribute, Predicate};
use asdi::idb::{Atom, Query, Term, Variable};
use asdi::Program;
use std::str::FromStr;

fn ancestor_example() {
    // See https://en.wikipedia.org/wiki/Datalog

    let mut ancestors = Program::default();

    let parent_predicate = Predicate::from_str("parent").unwrap();
    {
        let parent = ancestors
            .add_new_relation(
                parent_predicate.clone(),
                vec![Attribute::string(), Attribute::string()],
            )
            .unwrap();
        parent
            .add_as_fact(["xerces".into(), "brooke".into()])
            .unwrap();
        parent
            .add_as_fact(["brooke".into(), "damocles".into()])
            .unwrap();
    };

    let ancestor_predicate = Predicate::from_str("ancestor").unwrap();

    let var_x: Term = Variable::from_str("X").unwrap().into();
    let var_y: Term = Variable::from_str("Y").unwrap().into();
    let var_z: Term = Variable::from_str("Z").unwrap().into();

    ancestors
        .add_new_rule(
            ancestor_predicate.clone(),
            [var_x.clone(), var_y.clone()],
            [Atom::new(parent_predicate.clone(), [var_x.clone(), var_y.clone()]).into()],
        )
        .unwrap();
    ancestors
        .add_new_rule(
            ancestor_predicate.clone(),
            [var_x.clone(), var_y.clone()],
            [
                Atom::new(parent_predicate, [var_x.clone(), var_z.clone()]).into(),
                Atom::new(ancestor_predicate.clone(), [var_z, var_y]).into(),
            ],
        )
        .unwrap();

    ancestors
        .add_new_query(ancestor_predicate, ["xerces".into(), var_x])
        .unwrap();

    println!(">{}<", ancestors);
}

Changes

Version 0.2.3

• Added new "*=" operator for regular expressions
• Renamed the variants of LiteralInner/Literal to be Relational and Arithmetic to convey meaning, not just type.
• Renamed Relations to RelationSet and Rules to RuleSet.
• Renamed PredicateSet to NameReferenceSet and used for variables also; this also added AttributeNameRef type for clarity.
• Updated the highlight.js datalog language definition for comment and operator changes.
• Replaced more uses of the term "comparison (operator)?" with arithmetic literal
• Fixed more Clippy warnings.

Version 0.2.2

• Made changes to syntax to align more closely with traditional Datalog, as well as Soufflé:
  • using % instead of # for line comments,
  • added /* and */ for block comments,
  • removed the need for a @ prefix on the boolean constants true and false,
  • using . instead of @ for pragmas.
  • ASDI still uses separate assert and infer pragmas rather than Soufflé's single decl.
  • Also, to keep pragmas regular with other statements they end in a . whereas in Soufflé they do not.
• Fixed parsing errors in CSV and JSON files, mainly parsing strings (include/exclude quotes).

Version 0.2.1

• Added traits for consistency across types.
• Added a predicate cache to reduce duplication.
• Finished the file input and output for relations.
• Cleaned up the error module and added functions for error construction.

Version 0.2.0

• New internal structures and library layout.
• Less cloning, but still too much.
• Finished top-level documentation, more to come.

Version 0.1.0

• Not published, used for own verification only.

Version 0.1.0-dev

• Initial release, mostly to verify CI infrastructure through to crates.io