Modeling and Simulation (M&S) is widely used in various fields of engineering, manufacturing or process industry to investigate different system variants. An increasing problem of M&S is the complexity and variety of system variants. This concerns on the one hand the modeling effort and on the other hand the management of system variants in simulation studies. A general approach to the specification of different system variants is offered by the System Entity Structure (SES). It describes a set of system designs with different system structures and parameter configurations. In combination with a Model Base (MB), an SES can be used to describe different configurations of simulation models. The SES/MB framework and extended software architectures based on it define methods for the automated selection of system/model variants as well as for the generation and execution of simulation models. In this paper, the special descriptive element of the SES, the multi-aspect, is discussed. It is shown, how with hierarchically arranged multi-aspects certain forms of system variants can be specified very efficiently. Furthermore, a method for an automated derivation of system variants is presented in the context of hierarchical multi-aspects. This is important for the automation of simulation studies. For a practical illustration of the general method, it is presented using a problem from the process industry.