Deductive Database with Datalog, SQL, RA, TRC, DRC
The Datalog Educational System (DES) is a deductive database with Datalog, SQL, Relational Algebra, Tuple Relational Calculus and Domain Relational Calculus as query languages developed mainly for education. It can be used from most common Prolog interpreters over any supported OS and from portable executables (Windows, Linux and MacOS).
A Prolog expert system supporting querying and extending the knowledge base from a command-line interface using a format oriented on natural language, with the aim of being maintainable by the domain expert (i.e. without requiring programming skills).