  Graph products are characterized by the existence of non-trivial equivalence
relations on the edge set of a graph that satisfy a so-called square property.
We investigate here a generalization, termed RSP-relations. The class of graphs
with non-trivial RSP-relations in particular includes graph bundles.
Furthermore, RSP-relations are intimately related with covering graph
constructions. For K_23-free graphs finest RSP-relations can be computed in
polynomial-time. In general, however, they are not unique and their number may
even grow exponentially. They behave well for graph products, however, in sense
that a finest RSP-relations can be obtained easily from finest RSP-relations on
the prime factors.
