The Service implements OGC Filter Encoding 2.0 Encoding Standard with a set of comparison operators to facilitate the querying of geospatial features.
Service supports following operators: Logical operators: AND, OR, NOT.
Spatial operators: Within, DWithin, BBox, Intersects, Equals, Disjoint, Touches, Contains, Overlaps, Crosses, Beyond.
Value comparison operators: PropertyIsLike, PropertyIsNull, PropertyIsBetween, Property IsNil, PropertyIsEqualTo, PropertyIsNotEqualTo, PropertyIsLessThan, PropertyIsGreaterThan, PropertyIsLessThanOrEqualTo, PropertyIsGreaterThanOrEqualTo.
Reference
OGC Filter Encoding 2.0
https://www.ogc.org/standards/filter/