  The aim of this paper is to summarize some recently obtained relations
between the Ablowitz-Ladik hierarchy (ALH) and other integrable equations. It
has been shown that solutions of finite subsystems of the ALH can be used to
derive a wide range of solutions for, e.g., the 2D Toda lattice, nonlinear
Schr\"odinger, Davey-Stewartson, Kadomtsev-Petviashvili (KP) and some other
equations. Similar approach has been used to construct new integrable models:
O(3,1) and multi-field sigma models. Such 'universality' of the ALH becomes
more transparent in the framework of the Hirota's bilinear method. The ALH,
which is usually considered as an infinite set of differential-difference
equations, has been presented as a finite system of functional-difference
equations, which can be viewed as a generalization of the famous bilinear
identities for the KP tau-functions.

Exactly Solvable and Integrable Systems;Exactly Solvable and Integrable Systems