  Emulation has been successfully applied across a wide variety of scientific
disciplines for efficiently analysing computationally intensive models. We
develop known boundary emulation strategies which utilise the fact that, for
many computer models, there exist hyperplanes in the input parameter space for
which the model output can be evaluated far more efficiently, whether this be
analytically or just significantly faster using a more efficient and simpler
numerical solver. The information contained on these known hyperplanes, or
boundaries, can be incorporated into the emulation process via analytical
update, thus involving no additional computational cost. In this article, we
show that such analytical updates are available for multiple boundaries of
various dimensions. We subsequently demonstrate which configurations of
boundaries such analytical updates are available for, in particular by
presenting a set of conditions that such a set of boundaries must satisfy. We
demonstrate the powerful computational advantages of the known boundary
emulation techniques developed on both an illustrative low-dimensional
simulated example and a scientifically relevant and high-dimensional systems
biology model of hormonal crosstalk in the roots of an Arabidopsis plant.
