A newbie question regarding P

From: Uccai Siravas (uccai_siravas_at_yahoo.com)
Date: 12/08/03 

Date: 7 Dec 2003 21:58:42 -0800

If I understand correctly, every problem in NP can be reduced to SAT
(or any other NP-complete problem) using a polytime reduction.

Is this true of P also? That is, is there a known polytime problem
(call it A) to which each problem in P can be reduced using some
polytime reduction.

An example would be "all problem in P can be reduced to say 2-SAT"
In this case A is 2-SAT.

Are there any (accessible) work done on the characterization of P?

Uccai Siravas