· The structure of urban systems includes human and nonhuman organisms; abiotic components such as soil, water, land, climate, buildings, roads, and technological infrastructure; social institutions; politics and governance; and economic drivers—all of which interact to produce the observable functions of urban systems.

· Humans interact dynamically within social-ecological-technical/built system (SETS) components.

· Delineating boundaries and defining response units are crucial for empirical research, as is understanding the influences, material, and energy that cross boundaries.

· Urban ecosystem function emerges from the interactions, relationships, and feedbacks of system components.

· Urban systems are spatially heterogeneous and temporally dynamic.

· Linking urban system patterns with processes at multiple scales is a primary focus.

· Conceptual frameworks must work across multiple spatial and temporal scales.

· Conceptual frameworks must incorporate key, well-described drivers of urban system dynamics, including social, ecological, political, economic, and technical processes.

· The relationship among urban form, heterogeneous spatial structure, and system functions must be known to theorize and measure ecosystem services.

· Conceptual frameworks must be designed to enable comparative studies across cities.