DASH is a realization of the PGAS (partitioned global address space) model in the form of a C++ template library. Operator overloading is used to provide global-view PGAS semantics without the need for a custom PGAS (pre-) compiler. The DASH library is implemented on top of our runtime system DART, which provides an abstraction layer on top of existing one-sided communication substrates. DART contains methods to allocate memory in the global address space as well as collective and one-sided communication primitives. To support the development of applications that exploit a hierarchical organization, either on the algorithmic or on the hardware level, DASH features the notion of teams that are arranged in a hierarchy. Based on a team hierarchy, the DASH data structures support locality iterators as a generalization of the conventional local/global distinction found in many PGAS approaches.