Simple Features


Simple Features is a set of standards that specify a common storage and access model of geographic feature made of mostly two-dimensional geometries used by geographic information systems.
Is is formalized by both the Open Geospatial Consortium and the International Organization for Standardization.
The ISO 19125 standard comes in two parts. Part one, ISO 19125-1, defines a model for two-dimensional simple features, with linear interpolation between vertices, defined in a hierarchy of classes; this part also defines representation of geometry in text and binary forms. Part 2 of the standard, ISO 19125-2, defines an implementation using SQL. The OGC standards cover additionally implementations in CORBA and OLE/COM, although these have lagged behind the SQL one and are not standardized by ISO.
The ISO/IEC 13249-3 SQL/MM Spatial extends the Simple Features data model mainly with circular interpolations and adds other features like coordinate transformations and methods for validating geometries as well as Geography Markup Language support.

Standard documents

The geometries are also associated with spatial reference systems. The standard also specifies attributes, methods and assertions with the geometries. In general, a 2D geometry is simple if it contains no self-intersection. The specification defines DE-9IM spatial predicates and several spatial operators that can be used to generate new geometries from existing geometries.

Implementations

Part 2 of Simple Feature Access is implemented to varying degrees in:
The GDAL library implements the Simple Features data model in its OGR component. The Java-based deegree framework implements SFA and various other OGC standards.
GeoSPARQL is an OGC standard that is intended to allow geospatially-linked data representation and querying based on RDF and SPARQL by defining an ontology for geospatial reasoning supporting a small Simple Features RDFS/OWL vocabulary for GML and WKT literals.
As of 2012, various NoSQL databases had very limited support for "anything more complex than a bounding box or proximity search".