  For a free partial action of a group in a set we realize the associated
partial skew group ring as an algebra of functions with finite support over an
equivalence relation and we use this result to characterize the ideals in the
partial skew group ring. This generalizes, to the purely algebraic setting, the
known characterization of partial C*-crossed products as groupoid C*-algebras.
For completeness we include a new proof of the C* result for free partial
actions.
