Rel is a free, open-source, true relational database management system with an advanced query language called Tutorial D.
1. Rel is for learning, teaching, and exploring relational database concepts;
2. Rel is for discovering the power and expressiveness of a true relational language;
3. Rel is for learning, experimenting with, and using Tutorial D;
4. Rel is a prototype or "working blueprint" for future industrial-strength implementations of Tutorial D and other "D" languages;
5. Rel provides source code for experimenting with and/or examining interpreter and database engine internals.

Advantages of Rel and Tutorial D:
1. Tutorial D uses relation-valued variables - known as relvars - instead of the tables used in most database languages. This provides a way to manage information that is consistent with the most familiar elements - variables and values - of easy-to-learn but powerful programming languages.
2. Tutorial D supports nested relations, to provide flexibility in modeling data storage requirements and presenting complex query results.
3. Tutorial D provides a clean query syntax that exposes the simplicity, elegance, power, and composability of the underlying relational algebra.
4. Tutorial D queries do not depend on column order. This reduces the likelihood of programmer error and makes code more maintainable.
5. Tutorial D does not allow duplicate rows (tuples) or use NULLs, which helps ensure the predictability and consistency of query results.
6. Tutorial D supports advanced database constraints, which go beyond foreign key and "check" constraints in specifying controls on data consistency and integrity.
7. Tutorial D is more than a query language; it is a full programming language. It offers an intuitive and highly readable way to provide application functionality within a database, and provide database functionality within a programming language.
8. Tutorial D promotes code re-use, which improves maintainability, programmability, and opportunities for optimisation.
9. Tutorial D specifies an advanced type system for creating user-defined types of arbitrary complexity

Also this application is a prototype or "working blueprint" for future industrial-strength implementations of Tutorial'd and other "D" languages and it provides source code for experimenting with and / or examining interpreter and database engine internals.

Requirements:
* Java

The license of this software is Free, you can free download and free use this database management software.