Re: Character string relation and functional dependencies

Tegiri Nenashi wrote:

[...]

>Informally these FDs correspond to the length(), instr(), and substr()
>functions. So instead of talking about the class String with the
>length(), instr(), and substr() member functions, we can focus on a
>relation and functional dependencies....

Certainly. But we can't describe the full semantics of strings in that way. How do you represent concatenation?

Another difference is that database tables are finite and variable, while the set of strings is infinite and fixed. But your idea is used in theoretical papers, where concrete domains are sometimes introduced in terms of fixed infinite tables.

-- 
Reinier Post
TU Eindhoven