  Recognising that real-world optimisation problems have multiple
interdependent components can be quite easy. However, providing a generic and
formal model for dependencies between components can be a tricky task. In fact,
a PMIC can be considered simply as a single optimisation problem and the
dependencies between components could be investigated by studying the
decomposability of the problem and the correlations between the sub-problems.
In this work, we attempt to define PMICs by reasoning from a reverse
perspective. Instead of considering a decomposable problem, we model multiple
problems (the components) and define how these components could be connected.
In this document, we introduce notions related to problems with mutliple
interndependent components. We start by introducing realistic examples from
logistics and supply chain management to illustrate the composite nature and
dependencies in these problems. Afterwards, we provide our attempt to formalise
and classify dependency in multi-component problems.
