The presence API grants zones the ability to report whether or not a human is present within their geographic boundaries.
Factors are metrics by which presence can be determined. They are created at the ecosystem level and are available for use by the ecosystem's zones. The ability of an ecosystem's zones to detect presence may be enabled and disabled at will, and factors may be edited at any time.
Each factor has one value: whether it has detected presence (true) or not (false). It is these values with which zones interact, rather than the factors themselves. Although an ecosystem may have several different factor values available, zones may pick and choose which ones to incorporate into their detection.
Zones have three modes of presence detection:
local: only the direct factors of the zone are considered
descendants: only the factors of the child zones are considered
combined: both the zone's own factors and the factors of its children are considered
If presence detection is not desired for a particular zone, it's mode may be set to