WEB FEATURE SERVICE (WFS)
The Web Feature Service (WFS) is defined by the Open Geospatial Consortium (OGC) in order to provide the associated information of a stored feature within a vector coverage and according to the requested parameters of the query. It is a standard service which uses a communication interface to interact the served maps by the WMS standard. For instance, editing a served image or analyzing an image according to geographic criteria. The Aragon Government implements this service by GeoServer.
This standard defines three Basic actions:
- GetCapabilities it returns the formal description or service metadata in order to determine the available options. It is made up of two main elements: FeatureTypeList which lists the available geographic entities with the minimum demanded profile of information and FilterCapabilities which describes those expressions used to formulate spatial and alphanumeric queries.
- GetFeature It returns a geographic entity or feature previously input into the server, depending on the spatial query. It also depends on other suitable filters which are used by the WFS to take back the result of the search containing the entire geometry and the associated attributes. The main element of this operation is the action StoredQuery which is similar to the action GetFeatureById.
- DescribeFeatureType It returns an XML diagram describing the sort of data served by the WFS and pointing out the petition codes of the objects in queries or transactions.
WFS services are classified as non-transactional and transactional. The difference between these two types is that non-transactional WFS makes possible to consult and return geographic elements and transactional WFS also makes possible to create,eliminate and update them by the Transaction element.
The url to the formal description of the WFS provided by IDEAragon is the following:
A WFS client is able to download vector data, used to draw maps, spatial analysis and other actions. The integration of the WFS of IDEAragon can be carried out both from Web environments and thick SIG clients (pay software or freeware). Below, some examples of requests to the service from a thin-client (Web browser):