...
grid: a reference to a grid definition elsewhere in the YAML file
sources: a reference to one or more source sections - if this is a MapServer WMS, the source include includes both the reference to the source name in the YAML file (e.g. aerial_wms_2013) and the name of the layer or group in the map file (e.g. aerial2013)
cache: details of the cache itself, containing
type: the type of cache storage
filename: the location of the cache
...
This section defines the source of the data to be displayed and cached. The Sources section It will contain one or more sources, of which a single layer can reference one or more. The first line of the source will be used in the sources section of the layer as a reference. Each source will also have:
...