## Project Roadmap

This document outlines the implemented features and the future goals for the project.

> [!IMPORTANT]
> This roadmap is a work in progress and is subject to change.

### Core Features

- [x] Term representation (`Constant`, `Null`, `Variable`)
- [x] Atom structure (predicate with terms)
- [x] Database instance (set of ground atoms)
- [x] Tuple-generating dependencies (TGDs)
- [x] Rule builder with fluent API
- [x] Variable substitutions
- [x] Atom unification
- [x] Core chase algorithm
- [x] Restricted chase (trigger tracking for termination)
- [x] Existential variable support (labeled null generation)
- [x] Multi-atom rule bodies (conjunctive queries)
- [x] Multi-atom rule heads
- [x] Constants in rule patterns

### Chase Variants

- [x] Restricted chase (current implementation)
- [ ] Standard chase
- [ ] Oblivious chase
- [ ] Skolem chase
- [ ] Core chase (with homomorphism checks)
- [ ] Parallel chase

### Advanced Features

- [ ] Equality-generating dependencies (EGDs)
- [ ] Negative constraints (NCs)
- [ ] Stratified negation in rule bodies
- [ ] Disjunctive heads
- [ ] Aggregation support
- [ ] Recursion detection and optimization
- [ ] Termination analysis (weak acyclicity, joint acyclicity)

### Query Answering

- [ ] Boolean conjunctive query (BCQ) entailment
- [ ] Conjunctive query (CQ) answering
- [ ] Query rewriting
- [ ] Certain answer computation

### Performance Optimizations

- [ ] Predicate indexing (hash-based fact lookup)
- [ ] Semi-naive evaluation
- [ ] Magic sets transformation
- [ ] Incremental chase (delta rules)
- [ ] Memory-efficient null representation
- [ ] Parallel rule evaluation

### Parsing and I/O

- [ ] Datalog parser
- [ ] Rule file format (.dlog or similar)
- [ ] Fact import/export (CSV, JSON)
- [ ] SPARQL-like query syntax
- [ ] RDF/OWL integration

### Development and Testing

- [x] Unit tests (in-module)
- [x] Integration tests
- [ ] Property-based tests (QuickCheck/proptest)
- [ ] Regression tests
- [ ] Benchmarks
- [ ] Fuzzing

### Documentation and Tooling

- [ ] API documentation (rustdoc)
- [ ] User guide
- [ ] Example programs
- [ ] CLI interface
- [ ] REPL for interactive queries