Unified Modeling Language (UML) offers extensive possibilities to model static structure as well as dynamic behavior, both key domains of a complete system specification. UML, however, fails to clearly specify its semantics, in particular to coherently and consistently align the semantics of structure and behavior. The key idea of Model-Driven Development (MDD), which is to generate implementations from models, is hardly feasible due to the informally and therefore ambiguously defined semantics. The misalignment between the semantics of static structure and dynamic behavior, which both are required for a complete specification of a system, makes things even worse. This thesis is particularly concerned with the semantics of UML regarding t...