Geography Markup Language

Geography Markup Language (GML) is an XML based format for expressing geographical features, which can be natural or artificial. Natural geographical features include landforms such as terrain types and bodies of water, while engineered constructs, such as roads and bridges, are artificial. GML has been defined by the Open Geospatial Consortium (OGC), which is an international industry consortium consisting of companies, government agencies and universities. GML serves as a modeling language for geographic systems as well as an open interchange format for geographic transactions. A GML document describes generic geographic data sets that may contain points, lines and polygons. However, communities typically work together to define community-specific GML application schemas that support data interoperability in a specific application domain. For example, an application for city planning may define object types most relevant for that domain.

Web Feature Service

Web Feature Service (WFS) is an interface standard developed by the OGC. It provides a technology for exchanging geographical information in vector format over the Internet. WFS offers fine-grained access to geographic information at the level of geographical features and their properties. Web feature services allow clients to retrieve the data they are looking for, rather than retrieving a file that contains the data they are looking for. XML based GML is used as the default-encoding format for transporting the geographic features between a WFS server and a WFS client. The basic Web Feature Service allows querying and retrieval of features based on both spatial and non-spatial constraints. The HTTP protocol is used for transferring the WFS requests.

Transactional Web Feature Services

Transactional operations of the Web Feature Service 2.0 standard (WFS-T) allow creating, modifying, replacing and deleting features using the WFS interface. GML is used for encoding the geographic feature data between a WFS server and a WFS client, which is often a Geographic Information Services (GIS) product. The HTTP protocol is used for transferring these WFS requests which allows interaction in corporate networks and over the Internet.

Geosemantic query extensions in Profium Sense

With geosemantic extensions Sense allows optimized use of topological and spatial functions in SPARQLqueries. These functions allow restricting the query to semantic entities in a certain area, just crossing it, or within a certain distance from a geographic object. In addition to single coordinate points, Sense also manages lines and polygons. All this can be used within SPARQL queries in combination with non-spatial semantic filters.

Geosemantic extensions also make it possible to return geographic data in SPARQL query results aligned with the other data. This can be used for example for visualizing result sets on top of a map without invoking additional queries into spatial databases.