Managing variations of product portfolios and small lot sizes constitute some of the most important challenges in industrial automation today. Ever shorter development cycles require new tools to integrate all relevant corporate divisions from product design to production planning and quality control. In this paper we describe a formal modeling approach that allows to encapsulate properties of product variations on different levels. First, a specification decomposing the product into components and their respective ranges of variations is developed. Second, the capabilities of the production system are derived based upon principal production steps. In the third step, the two descriptions have to be mapped to obtain a production sequence for an individual product variant. Therefore, the specifications are expressed in the same unified modeling language (UML) that can represent both structural properties on a class level and interactions of objects. This approach is implemented on a modular production line for an exemplary assembling process comprised of different handling tasks. As a future direction of research, formal methods known from theoretical computer science will be incorporated, e.g. to check model variants and production steps for compatibility.