Editing Web Feature Service (section)

==Overview ==
The WFS specification defines interfaces for describing data manipulation operations of geographic features. Data manipulation operations include the ability to:

* get or query features based on spatial and non-spatial constraints
* create a new feature instance
* delete a feature instance
* update a feature instance

The basic Web Feature Service allows querying and retrieval of features.  A transactional Web Feature Service (WFS-T) allows creation, deletion, and updating of features.

A WFS describes discovery, query, or data transformation operations. The client generates the request and posts it to a web feature server using HTTP. The web feature server then executes the request. The WFS specification uses HTTP as the distributed computing platform, although this is not a hard requirement.

There are two encodings defined for WFS operations:
* [[XML]] (amenable to HTTP POST, or [[SOAP]])
* Key/value pairs (encoded in HTTP GET [[query string]]s, to perform [[remote procedure call]]s)<ref>{{cite web| url=http://portal.opengeospatial.org/files/?artifact_id=36263&format=pdf | access-date=2023-10-31 | title=WCS Extension -- KVP Protocol}}</ref>

In the taxonomy of [[Web Services]], WFS is best categorized as a non-RESTful RPC type service.

=== Communication models===
The WFS Web Feature Services or Web Feature Server specification supports two communication models:
*Stateless Request Reply
*Pub/Sub
::A messaging system in which clients address messages to a specific node in a content hierarchy, called a topic. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a node's multiple publishers to its multiple subscribers. Messages are generally not persistent and will only be received by subscribers who are listening at the time the message is sent. A special case known as a “durable subscription” allows subscribers to receive messages sent while the subscribers are not active. (Source: [http://java.sun.com/j2ee/1.4/docs/glossary.html Oracle Technology Network for Java Developers | Oracle Technology Network | Oracle])

The Web Notification Service (WNS) is one of the implementation specifications for the Pub/Sub model. Regardless of the model, [[Uniform Resource Locator|URL]] format is used and specified in the WFS specification. At this time there are no open-standard implementations of WNSs. Vendors plan to release implementations once the standard has been ratified.

===Data ===
{{main|Geography Markup Language}}

Data passed between a Web Feature Server and a client is encoded with [[Geography Markup Language]] (GML), an XML dialect which can be used to model geographic features.

The 1.0.0 version of the WFS specification requires the use of GML version 2.1.2, while the 1.1.0 version of the WFS specification requires the use of GML version 3.1.1.  For both versions of the WFS specification, an arbitrary number of other encodings can also be defined, in addition to the required GML 2.1.2 or 3.1.1 format (for 1.0.0 and 1.1.0 respectively).

GML 2.1.2 contains encoding support for basic geometric 'primitives':  points, lines, polygons, etc.

GML 3.1.1 contains encoding support for more advanced geometric representations:  curves, surfaces, multi-dimensions (time, elevation, multi-band imagery).  In addition, GML 3.1.1 includes encoding support for topologically integrated datasets.