Abstract:
Let $\mathcal{A}$ be a computable structure and let $R$ be an additional relation on its domain. We establish a necessary and sufficient condition for the existence of an isomorphic copy $\mathcal{B}$ of $\mathcal{A}$ such that the image of $R$ ($\lnot R$) is $h$-simple ($h$-immune) relative to $\mathcal{B}$.