.. _wfs:

*****************************************************************************
 WFS
*****************************************************************************

WFS is an Open Geospatial Consortium (OGC) specification.  For more information about the format itself, see: http://www.opengeospatial.org/standards/wfs

WFS allows a client to retrieve geospatial data encoded in Geography Markup 
Language (GML) from multiple Web Feature Services.  GML is built on the 
standard web language XML.

WFS differs from the popular Web Map Service (WMS) specification in that 
WFS returns a subset of the data in valid GML format, not just a graphic 
image of data.


Capabilities
-------------------

Requesting the capabilities using the GetCapabilities request to a WFS server returns an XML document showing what layers and  projections are available, etc.
Example of a WFS GetCapabilities URL:



	http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=GetCapabilities

Example of the Resulting XML from GetCapabilties:

::

	...
	<FeatureTypeList>
	  <Operations>
	    <Query/>
	  </Operations>
	    <FeatureType>
		<Name>continents</Name>
		<Title>World continents</Title>
		<SRS>EPSG:4326</SRS>
		<LatLongBoundingBox minx="-180" miny="-90" maxx="180" maxy="83.6274"/>
	    </FeatureType>
	    <FeatureType>
		<Name>cities</Name>
		<Title>World cities</Title>
		<SRS>EPSG:4326</SRS>
		<LatLongBoundingBox minx="-178.167" miny="-54.8" maxx="179.383" maxy="78.9333"/>
	    </FeatureType>
	</FeatureTypeList>
	...

Data Access / Connection Method
---------------------------------

*  WFS access is a core MapServer feature. MapServer currently supports 
   WFS version 1.0.0

*  The CONNECTIONTYPE WFS parameter must be used.

*  WFS layers can be requested through a layer in a map file, or you can 
   request the GML directly through the browser with a GetFeature 
   request.  You can specify a specific layer with the TypeName 
   request.  In a map file the name/value pairs should be put 
   into a METADATA object.

*  You can limit the number of features returned in the GML by using 
   the MaxFeatures option (e.g. &MAXFEATURES=100).

Example of a WFS Request Directly Through the Browser:

The following URL requests the GML for the layer continents.  (see the 
GetCapabilities above for the possible layers available on this 
test server) .  The URL is all one line, broken up here for readability (click `here <http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=getfeature&TYPENAME=continents&MAXFEATURES=100>`__ for a working link).
::
	
	http://demo.mapserver.org/cgi-bin/wfs?
	SERVICE=WFS&
	VERSION=1.0.0&
	REQUEST=getfeature&
	TYPENAME=continents&
	MAXFEATURES=100

Map File Example
----------------

.. code-block:: mapfile

	LAYER
	  NAME "continents"
	  TYPE POLYGON
	  STATUS ON
	  CONNECTION "http://demo.mapserver.org/cgi-bin/wfs?"
	  CONNECTIONTYPE WFS
	  METADATA
	    "wfs_typename"          "continents"
	    "wfs_version"           "1.0.0"
	    "wfs_connectiontimeout" "60"
	    "wfs_maxfeatures"       "10"
	  END
	  PROJECTION
	    "init=epsg:4326"
	  END
	  CLASS
	    NAME "Continents"
	    STYLE
	      COLOR 255 128 128
	      OUTLINECOLOR 96 96 96 
	    END
	  END
	END # Layer