This conceptual system should contain the technologies of interest and their interactions with upstream, downstream, and parallel unit processes. Notably, the system does not need to be limited to the boundary of any specific physical system, but it can include any related processes that may be impacted by changes to QSD inputs. In selecting the system boundary, an "allinclusive" approach would involve all upstream and downstream unit processes that interact directly or indirectly with the technologies. However, this approach may result in the inclusion of unit processes that are inconsequential to system sustainability, add unnecessary layers of complexity, and introduce sources of uncertainty that demand additional resources to evaluate.