D1.1 Technology survey: Prospective and challenges - Revised version (2018)
7 Standards: INSPIRE and OGS
7.2 OGC standards
OGC – Open Geospatial Consortium is an international not for profit organization involved in the elaboration of open standards for the global geospatial community. These standards describe interfaces or encodings used by software developers to build open products and services. In particular, OGC Web Services (OWS) standards are dedicated to Web applications.
For example, WMS (Web Map Service) delivers spatial data (maps) as images, WFS (Web Feature Services) provides maps as vector data (features), while WPS (Web Processing Service) is standard for geospatial processing, such as polygon overlays. SensorML (Sensor Model Language) can be used to describe a large variety of sensors and facilitate sensors discovery and geolocation, processing sensor observations, subscribe to sensor alerts or program the sensor.
WaterML (Water Markup Language) is used for standard representation of hydrological time series data in XML format, while GML (Geography Markup Language) does the same thing for geographical information. Such representations use the textual format and can be understood by human readers. They have behind schemas descriptions that can be used by programs to understand the semantics of data, and process these data without human intervention (the approach is called Semantic Web).
Some standards are combinations of different technologies. For example, the Semantic Sensor Web (SSW) combines sensors and Semantic Web technologies so that software services can access sensors and their observations. Also, the Semantic Sensor Network (SSN) ontology offers expressive representation of sensors, observations, and knowledge of the environment.
OGC is continuously elaborating new standards, many specifications being in phase of adoption by the OGC membership as official OGC standards.
OGC standards are based on client-server architectures. The REST (REpresentational State Transfer) architecture considers that the system is a collection of addressable resources (e.g. with URLs), each resource offering a specific Web service to clients. To invoke a service, the client sends a HTML message (GET, PUT, DELETE, POST) to a specific resource, which executes the software service and returns the actual state that is represented by the service’s result.