This standard is a generic filter grammar that can be used to specify how resource instances in a source collection of any item type, including features, can be filtered to identify a results set. Typically, CQL2 is used in query operations to identify the subset of resources, such as features, that should be included in a response document.
Request For Comment (RFC)
OGC Seeks Public Comment on Candidate OGC SensorThings API Extension: WebSub Asynchronous Messaging Standard