About the code reduction algorithm

Question

Codd Algorithm converts an expression into relational calculus of a tuple into relational algebra. I'd like to know:

• Is there a standard implementation of the algorithm?
• is this algorithm used anywhere? (Only SQL and options are needed for the industry, I'm not sure about theorists of the database in academia).
• What is the difficulty of cutting?

Answer 1

Implementation of the Codd algorithm should be fairly easy (*), but:

Converting an expression in one language to an expression in another language requires someone to know what “another language” is. You can say?

, - , . "" ?

, , .

(*), , , <universalquantification> , < > , < > , <cartesian> ,...