Editing Web Feature Service (section)

=== 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.