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Simple Features (officially Simple Feature Access) is a set of standards that specify a common storage and access model of geographic feature made of mostly two-dimensional geometries (point, line, polygon, multi-point, multi-line, etc.) used by
geographic information system A geographic information system (GIS) is a type of database containing Geographic data and information, geographic data (that is, descriptions of phenomena for which location is relevant), combined with Geographic information system software, sof ...
s. It is formalized by both the Open Geospatial Consortium (OGC) and the International Organization for Standardization (ISO). The ISO 19125 standard comes in two parts. Part 1, ISO 19125-1 (SFA-CA for "common architecture"), 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 (WKT) and binary (WKB) forms. Part 2 of the standard, ISO 19125-2 (SFA-SQL), defines a "SQL/MM" language binding API for SQL under the prefix "SF_". The
open access Open access (OA) is a set of principles and a range of practices through which research outputs are distributed online, free of access charges or other barriers. With open access strictly defined (according to the 2001 definition), or libre op ...
OGC standards cover additionally APIs for CORBA and OLE/
COM Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level d ...
, although these have lagged behind the SQL one and are not standardized by ISO. There are also adaptations to other languages covered below. The ISO/IEC 13249-3 SQL/MM Spatial extends the Simple Features data model mainly with circular interpolations (e.g. circular arcs) and adds other features like coordinate transformations and methods for validating geometries as well as Geography Markup Language support.


Details


Part 1

The geometries are associated with spatial reference systems. The standard also specifies attributes, methods and assertions with the geometries, in the object-oriented style. 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.


Part 2

Part 2 is an SQL binding to Part 1, providing a translation of the interface to non-object-oriented environments. For example, instead of a someGeometryObject.isEmpty() as in Part 1, SQL/MM uses a ST_IsEmpty(...) function in SQL.


Spatial

The spatial extension adds the datatypes "Circularstring", "CompoundCurve", "CurvePolygon", "PolyhedralSurface", the last of which is also included into the OGC standard. It also defines the SQL/MM versions of these types and operations on them.


Implementations

Direct implementations of Part 2 (SQL/MM) include: * MySQL Spatial Extensions. Up to MySQL 5.5, all of the functions that calculate relations between geometries are implemented using bounding boxes not the actual geometries. Starting from version 5.6, MySQL offers support for precise object shapes. * MonetDB/GIS extension for MonetDB. * PostGIS extension for
PostgreSQL PostgreSQL (, ), also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. It was originally named POSTGRES, referring to its origins as a successor to the In ...
, also supporting some of the SQL/MM Spatial features. * SpatiaLite extension for SQLite * Oracle Spatial, which also implements some of the advanced features from SQL/MM Spatial. *
IBM Db2 Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON a ...
Spatial Extender and IBM Informix Spatial DataBlade. * Microsoft SQL Server since version 2008, with significant additions in the 2012 version. * SAP
Sybase IQ SAP IQ (formerly known as SAP Sybase IQ or Sybase IQ; IQ for Intelligent Query) is a column-based, petabyte scale, relational database software system used for business intelligence, data warehousing, and data marts. Produced by Sybase Inc., now ...
. * SAP HANA as of 1.0 SPS6. Adaptations include: * Implementations of the CORBA and OLE/COM interfaces detailed above are mainly produced by commercial vendors maintaining legacy technology. * R: The sf package implements Simple Features and contains functions that bind to GDAL for reading and writing data, to GEOS for geometrical operations, and to PROJ for projection conversions and datum transformations. * The GDAL library implements the Simple Features data model in its OGR component. * The Java-based deegree framework implements SFA (part 1) 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 (as well as DE-9IM and RCC8) RDFS/ OWL vocabulary for GML and WKT literals. As of 2012, various
NoSQL A NoSQL (originally referring to "non- SQL" or "non-relational") database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Such databases have existed ...
databases had very limited support for "anything more complex than a bounding box or proximity search".


See also

* DE-9IM *
Well-known text Well-known text (WKT) is a text markup language for representing vector geometry objects. A binary equivalent, known as well-known binary (WKB), is used to transfer and store the same information in a more compact form convenient for computer proc ...


References


External links


Simple Features SWG


Standard documents

* ISO/IEC: *

** ttp://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=40115 ISO 19125-2:2004 Geographic information -- Simple feature access -- Part 2: SQL option* OpenGIS *
OpenGIS Implementation Specification for Geographic information - Simple feature access - Part 1: Common architecture (05-126, 06-103r3, 06-103r4)
current version 1.2.1 *
OpenGIS Simple Feature Access - Part 2: SQL Option (99-054, 05-134, 06-104r3, 06-104r4)
current version 1.2.1, formerly OpenGIS Simple Features mplementation Specificationfor SQL *
OpenGIS Simple Features Implementation Specification for CORBA (99-054)
current version 1.0 *
OpenGIS Simple Features Implementation Specification for OLE/COM (99-050)
current version 1.1 {{ISO standards Geographic information systems Open Geospatial Consortium ISO/TC 211 Spatial database management systems