“…It is outside the scope of this short Note to explain this notion here, and we refer the reader to the textbook 13 and the lecture notes 12,14 and the historical references therein. Importantly, based on these scattering maps we need to design structurepreserving algorithms, which are typically of front tracking type, or of shock capturing type with well-controlled dissipation 15 . The algorithms are designed in order to mimic analytical properties at the discrete level and this requirement may take very different flavors: divergence form, spacelike decay, timelike decay shock-capturing, energy balance laws, asymptotics on singularities, etc.…”