Mikito Harakiri wrote:
>
> Returning to OP question:
>
> "AFAIK the expressive power of modern state-of-art database software
> like Oracle and PostgreSQL still falls far behind first-order logic:
> it essentially doesn't have functors or recursion."
>
> In SQL DBMSs aren't "function symbols" just UDFs (aka stored
> procedures), then? Including fairly recent incarnations: table
> functions?
The way that function symbols are interpreted in Prolog and what gives
them their expressive power in combination with recursion is more like
what you would call a tuple constructor. So a term like f(x,y)
represents a binary tuple with fields x and y and a label f that
distinguishes it from g(x,y). So a better analogue would be user-defined
record types where the type system allows arbitrary deep nesting or
recursive types.
Received on Mon May 16 2005 - 15:05:23 CDT
