Relational calculi in a deductive system

This work describes the addition of relational calculus languages in the deductive database system DES. Based on first-order logic, such languages admit a clean logical reading of queries, providing truly declarativeness, in contrast to other languages based on logic such as Prolog (a classical language used to build expert systems). Interesting properties as termination (for finite relations) and recursion are ensured because the DES deductive engine is used for solving relational calculus queries. Recursion in particular opens a brand new ream of applications (social networks, data warehouses, ...) for relational calculus languages which were unmanageable up to now. Since the DES system was targeted at teaching, we have also make a special emphasis on providing a practical system for students by providing appropriate syntax error feedback in a system supporting different languages (including relational algebra, SQL and Datalog).