The exact discrete model satisfied by equispaced data
generated by a linear stochastic differential equations
system is derived by a method that does not imply restrictions
on observed discrete data per se. The method involves integrating
the solution of the continuous time model in state space
form and a nonstandard change in the order of three types
of integration, facilitating the representation of the
exact discrete model as an asymptotically time-invariant
vector autoregressive moving average model. The method
applying to the state space form is general and is illustrated
using the prototypical higher order model for mixed stock
and flow data discussed by Bergstrom (1986, Econometric
Theory 2, 350–373).