system of second order differential equations are the time integration schemes of Newmark and the Hilbert-Hughes-Taylor scheme. The modal domain concerns component mode synthesis (CMS) techniques such as the Craig-Bampton, Rubin and McNeal method. These methods provide efficient modal reduction bases and assembly techniques for numerical models in the physical domain. The frequency domain is more popularly known as Frequency Based Substructuring (FBS). Based on the classic formulation of Jetmundsen et al. and the reformulation of De Klerk et al., it has become the most commonly used domain for substructuring, because of the ease of expressing the differential equations of a dynamical system (by means of Frequency Response Functions, FRFs) and the convenience of implementing experimentally obtained models. The time domain refers to the recently proposed concept of Impulse Based Substructuring (IBS), which expresses the behaviour of a dynamic system using a set of Impulse Response Functions (IRFs). The state-space domain, finally, refers to methods proposed by Sjövall et al. that employ system identification techniques common to control theory. An overview of the governing equations of the five herementioned domains is presented in the table below. As dynamic substructuring is a domain-independent toolset, it is applicable to the dynamic equations of all domains. In order to establish substructure assembly in a particular domain, two interface conditions need to be implemented. This is explained next, followed by a few common substructuring techniques. Interface Conditions To establish substructuring coupling / decoupling in each of the above-mentioned domains, two conditions should be met: Coordinate compatibility, i.e. the connecting nodes of two substructures should have equal interface displacement. Force equilibrium, i.e. the interface forces between connecting nodes have equal magnitude and opposing sign. These are the two essential conditions that keep substructures together, hence allow to construct an assembly of multiple components. Note that the conditions are comparable with Kirchhoff's laws for electric circuits, in which case similar conditions apply to currents and voltages though/over electric components in a network; see also Mechanical–electrical analogies. Substructure connectivity Consider two substructures A and B as depicted in the figure. The two substructures comprise a total of six nodes; the displacements of the nodes are described by a set of Degrees of Freedom (DoFs). The DoFs of the six nodes are partitioned as follows: DoFs of the internal nodes of substructure A; DoFs of the coupling nodes of substructures A and B, i.e. interface DoFs; DoFs of