  Fractional-step methods are a popular and powerful divide-and-conquer
approach for the numerical solution of differential equations. When the
integrators of the fractional steps are Runge--Kutta methods, such methods can
be written as generalized additive Runge--Kutta (GARK) methods, and thus the
representation and analysis of such methods can be done through the GARK
framework. We show how the general Butcher tableau representation and linear
stability of such methods are related to the coefficients of the splitting
method, the individual sub-integrators, and the order in which they are
applied. We use this framework to explain some observations in the literature
about fractional-step methods such as the choice of sub-integrators, the order
in which they are applied, and the role played by negative splitting
coefficients in the stability of the method.
