  Long time ago, C.N. Yang proposed a model of noncommutative spacetime that
generalized the Snyder model to a curved background. In this paper we review
his proposal and the generalizations that have been suggested during the years.
In particular, we discuss the most general algebras that contain as subalgebras
both de Sitter and Snyder algebras, preserving Lorentz invariance, and are
generated by a two-parameter deformation of the canonical Heisenberg algebra.
We also define their realizations on quantum phase space, giving explicit
examples, both exact and in terms of a perturbative expansion in the
deformation parameters.
