Executable Domain Specific Modeling Languages (xDSML) opens many possibilities in terms of early verification and validation (V&V) of systems, including the use of dynamic V&V approaches. Such approaches rely on the notion of execution trace, i.e. the evolution of a system during a run. To benefit from dynamic V&V approaches, it is therefore necessary to characterize what is the structure of the executions traces of a given xDSML. Our goal is to provide an approach to design trace metamodels for xDSMLs. We identify seven problems that must be considered when modeling execution traces, including concurrency, modularity, and scalability. Then we present our envisioned approach to design scalable multidimensional trace metamodels for xDSMLs. Our work in progress relies on the dimensions of a trace (i.e. subsets of mu- table elements of the traced model) to provide an original structure that faces the identified problems, along with a trace API to manipulate them.