M\"obius invariant integrable lattice equations associated with KP and 2DTL hierarchies

Integrable lattice equations arising in the context of singular manifold equations for scalar, multicomponent KP hierarchies and 2D Toda lattice hierarchy are considered. These equation generate the corresponding continuous hierarchy of singular manifold equations, its B\"acklund transformations and different forms of superposition principles. They possess rather special form of compatibility representation. The distinctive feature of these equations is invariance under the action of M\"obius transformation. Geometric interpretation of these discrete equations is given.