In this chapter we will highlight modeling entities which serve as abstraction vehicles for a TCAD user who wants to perform thorough investigations on an IC fabrication technology, either process-, device-, or interconnect simulation, and combinations of them. The presented concepts do in no way require features of specific simulation tools. Particularly, they are intended to implement high-level abstractions independent from individual simulation tools. Modeling entities are outlined that represent simulation tools, sequences of them, and networks of simulation tools.