.. index:: 
   single: WFS Server

.. _wfs_server:

*****************************************************************************
 WFS Server
*****************************************************************************

:Author: Jean-François Doyon
:Contact: jdoyon at nrcan.gc.ca
:Author: Jeff McKenna
:Contact: jmckenna at gatewaygeomatics.com
:Revision: $Revision$
:Date: $Date$

.. contents::
    :depth: 2
    :backlinks: top
    
Introduction
============

A WFS ( Web Feature Service ) publishes feature-level geospatial data
to the web.  This means that instead of returning an image, as
MapServer has traditionally done, the client now obtains fine-grained
information about specific geospatial features of the underlying data,
at both the geometry AND attribute levels. As with other OGC
specifications, this interface uses XML over HTTP as it's delivery
mechanism, and, more precisely, GML (Geography Markup Language), which
is a subset of XML.

WFS-Related Information
-----------------------

Here are some WFS related links (including a newly added OGC services
workshop with MapServer). Since these are highly detailed technical
specifications, there is no need to read through them in their
entirety to get a MapServer WFS up and running. It is still
recommended however to read them over and get familiar with the basics
of each of them, in order to understand how it all works:

- The `OGC Web Feature Service Implementation Specification`_.

- The `Geography Markup Language Implementation Specification`_.

- MapServer `OGC Web Services Workshop package`_. 

Working knowledge of MapServer is of course also required.

Software Requirements
---------------------

In order to enable MapServer to serve WFS, it MUST be compiled against
certain librairies:

- PROJ.4: The reprojection library. Version 4.4.3 or greater is required.

- GDAL/OGR: I/O support libraries. Version 1.1.8 or greater is required.

Please see the MapServer :ref:`UNIX Compilation and Installation HowTo
<unix>` for detailed instructions on compiling mapserver with support
for these libraries and features.  For Windows users, the `MS4W`_
installer comes ready to serve both WFS and WMS.

.. index:: 
   pair: WFS Server; GML

Versions of GML Supported
-------------------------

MapServer can output both GML2 and GML3.  By default MapServer serves
GML2.  You can test this by adding an 'OUTPUTFORMAT' parameter to a
GetFeature request, such as:

- `GML2 request output`_
- `GML3 request output`_

For a detailed discussion on the versions supported, see `bug#884`_.


.. index:: 
   pair: WFS Server; Mapfile

Configuring your MapFile to Serve WFS layers
============================================

Much as in the WMS support, WFS publishing is enabled by adding
certain magic METADATA keyword/value pairs to a MapFile.

MapServer will serve and include in its WFS capabilities only the
layers that meet the following conditions:

- Data source is of vector type (Shapefile, OGR, PostGIS, SDE, SDO, ...)

- LAYER NAME must be set. Layer names must start with a letter when
  setting up a WFS server (layer names should not start with a digit
  or have spaces in them).

- LAYER TYPE is one of: LINE, POINT, POLYGON

- The "wfs_onlineresource" metadata:

  The wfs_onlineresource metadata is set in the map's web object
  metadata and specifies the URL that should be used to access your
  server. This is required for the GetCapabilities output. If
  wfs_onlineresource is not provided then MapServer will try to
  provide a default one using the script name and hostname, but you
  shouldn't count on that too much. It is strongly recommended that
  you provide the wfs_onlineresource metadata.

  See section 12.3.3 of the `WFS 1.0.0 specification`_ for the whole
  story about the online resource URL. Basically, what you need is a
  complete HTTP URL including the http:// prefix, hostname, script
  name, potentially a "map=" parameter, and and terminated by "?" or
  "&".

  Here is a valid online resource URL:

  ::
  
     http://my.host.com/cgi-bin/mapserv?map=mywfs.map&
          
  By creating a wrapper script on the server it is possible to hide
  the "map=" parameter from the URL and then your server's online
  resource URL could be something like:

  ::
  
     http://my.host.com/cgi-bin/mywfs?
          
  This is covered in more detail in the "More About the Online
  Resource URL" section of the :ref:`WMS Server <online_resource_wms>`
  document.

- The "wfs_enable_request" metadata (see below).



Example WFS Server Mapfile
--------------------------

The following is an example of a bare minimum WFS Server mapfile. Note
the comments for the required parameters.

.. code-block:: mapfile

      MAP
        NAME "WFS_server"
        STATUS ON
        SIZE 400 300
        SYMBOLSET "../etc/symbols.txt"
        EXTENT -180 -90 180 90
        UNITS DD
        SHAPEPATH "../data"
        IMAGECOLOR 255 255 255
        FONTSET "../etc/fonts.txt"


        #
        # Start of web interface definition
        #
        WEB
          IMAGEPATH "/ms4w/tmp/ms_tmp/" 
          IMAGEURL "/ms_tmp/"
          METADATA
            "wfs_title"          "WFS Demo Server for MapServer" ## REQUIRED
            "wfs_onlineresource" "http://demo.mapserver.org/cgi-bin/wfs?" ## Recommended
            "wfs_srs"            "EPSG:4326 EPSG:4269 EPSG:3978 EPSG:3857" ## Recommended
            "wfs_abstract"       "This text describes my WFS service." ## Recommended
            "wfs_enable_request" "*"  # necessary
          END
        END

        PROJECTION
          "init=epsg:4326"
        END

        #
        # Start of layer definitions
        #

        ##################
        # World Continents
        ##################
        LAYER 
          NAME "continents"
          METADATA
            "wfs_title"         "World continents" ##REQUIRED
            "wfs_srs"           "EPSG:4326" ## REQUIRED
            "gml_include_items" "all" ## Optional (serves all attributes for layer)
            "gml_featureid"     "ID" ## REQUIRED
            "wfs_enable_request" "*"
          END  
          TYPE POLYGON
          STATUS ON
          DATA 'shapefile/countries_area'
          PROJECTION
            "init=epsg:4326"
          END
          CLASS
            NAME 'World Continents'
            STYLE
              COLOR 255 128 128
              OUTLINECOLOR 96 96 96      
            END
          END
        END #layer

      END #mapfile

.. index:: 
   pair: WFS Server; SRS

Rules for Handling SRS in MapServer WFS
---------------------------------------

The OGC WFS 1.0 specification doesn't allow a layer (feature type)
to be advertised in more than one SRS.  Also, there is no default SRS
that applies to all layers by default.  However, it is possible to
have every layer in a WFS server advertised in a different SRS.

The OGC WFS 1.1 specification allows more than one SRS to be
advertised, and one of the SRSs will be advertised as the default SRS
(the default SRS will be the first in the list specified in the
`METADATA` `wfs_srs` / `ows_srs`).

Here is how MapServer decides the SRS to advertise and use for each
layer in your WFS:

- If a top-level map SRS is defined then this SRS is used and applies
  to all layers (feature types) in this WFS. In this case the SRS of
  individual layers is simply ignored even if it is set.

- If no top-level map SRS is defined, then each layer is
  advertised in its own SRS in the capabilities.

.. note::
  By "SRS is defined", we mean either the presence of a PROJECTION
  object defined using an EPSG code, or of a `wfs_srs` / `ows_srs`
  metadata at this level.

.. note::
   At the map top-level the `wfs_srs` / `ows_srs` metadata value takes
   precedence over the contents of the :ref:`PROJECTION` block.

At the layer level, if both the `wfs_srs` / `ows_srs` metadata and the
PROJECTION object are set to different values, then the `wfs_srs` /
`ows_srs` metadata defines the projection to use in advertising this
layer (assuming there is no top-level map SRS), and the PROJECTION
value is assumed to be the projection of the data. So this means that
the data would be reprojected from the PROJECTION SRS to the one
defined in the `wfs_srs` / `ows_srs` metadata before being served to
WFS clients.

Confusing? As a rule of thumb, simply set the `wfs_srs` / `ows_srs` at
the map level (in web metadata) and never set the `wfs_srs` /
`ows_srs` metadata at the layer level and things will work fine for
most cases.

Axis Orientation in WFS 1.1
---------------------------

The axis order in previous versions of the WFS specifications was to
always use easting (x or lon ) and northing (y or lat).  WMS 1.1
specifies that, depending on the particular SRS, the x axis may or may
not be oriented West-to-East, and the y axis may or may not be
oriented South-to-North. The WFS portrayal operation shall account for
axis order. This affects some of the EPSG codes that were commonly
used such as ESPG:4326.  The current implementation makes sure that
coordinates returned to the server for the GetFeature request reflect
the inverse axis orders for EPSG codes between 4000 and 5000.

Test Your WFS Server
--------------------

Validate the Capabilities Metadata
**********************************

OK, now that we've got a mapfile, we have to check the XML
capabilities returned by our server to make sure nothing is missing.

Using a web browser, access your server's online resource URL to which
you add the parameter "REQUEST=GetCapabilities" to the end, e.g.

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

If everything went well, you should have a complete XML capabilities
document.  Search it for the word "WARNING"... MapServer inserts XML
comments starting with "<!--WARNING: " in the XML output if it detects
missing mapfile parameters or metadata items. If you notice any
warning in your XML output then you have to fix all of them before you
can register your server with a WFS client, otherwise things are
likely not going to work.

.. note::
  The SERVICE parameter is required for all WFS requests.  When a
  request happens, it is passed through WMS, WFS, and WCS in MapServer
  (in that order) until one of the services respond to it.

Test With a GetFeature Request
******************************

OK, now that we know that our server can produce a valid XML
GetCapabilities response we should test the GetFeature request. Simply
adding
"SERVICE=WFS&VERSION=1.0.0&REQUEST=GetFeature&TYPENAME=yourlayername1,yourlayername2"
to your server's URL should return the GML associated with those
layers.

http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=getfeature&TYPENAME=continents&MAXFEATURES=100

Test with a Real Client
***********************

If you have access to a WFS client, then register your new server's
online resource with it and you should be off and running.

If you don't have your own WFS client installed already, here are a
few pointers:

- MapServer itself can be used as a WFS client, see the :ref:`WFS
  Client HowTo <wfs_client>`.

- `Quantum GIS`_ is a full GIS package which includes WFS client
  support. (recommended)

- `Deegree`_ provides a WFS client.

- `uDig`_ can add layers from WMS/WFS servers.

- The `owsview`_ Viewer Client Generator is an online application that
  allows users to validate WFS Capabilities XML (it does not allow you
  to view WFS data).
  
Support for GET and POST Requests
*********************************

Starting from version 4.2 MapServer supports XML-encoded POST requests
and GET requests. The default in MapServer is POST.

Support for Filter Encoding
***************************

Starting from version 4.2 MapServer supports Filter Encoding (FE) in
WFS GetFeature requests. For more information on the server side of
Filter Encoding see the :ref:`Filter Encoding HowTo
<filter_encoding>`.

MapServer WFS Extensions
************************

**STARTINDEX**
  In addition to the MAXFEATURES=n keyword, MapServer also supports a
  STARTINDEX=n keyword in WFS GetFeature requests.  This can be used
  to skip some features in the result set and in combination with
  MAXFEATURES provides for the ability to use WFS GetFeature to page
  through results.  Note that STARTINDEX=1 means start with the first
  feature, skipping none.

**OUTPUTFORMAT**
  Normally OUTPUTFORMAT should be GML2 for WFS 1.0 and either
  "text/xml; subtype=gml/2.1.2" or "text/xml; subtype=gml/3.1.1" for
  WFS 1.1.  However as an extension to the specification, it is also
  possible to configure MapServer for a variety of other feature
  output formats.  This is discussed in some detail in the :ref:`OGR
  Output <ogr_output>` document.

.. index:: 
   pair: WFS; Metadata

Reference Section
=================

The following metadata are available in the setup of the WFS Server
mapfile:

.. note::
  Each of the metadata below can also be referred to as 'ows_*'
  instead of 'wfs_*'.  MapServer tries the 'wfs_*' metadata first, and
  if not found it tries the corresponding 'ows_*' name. Using this
  reduces the amount of duplication in mapfiles that support multiple
  OGC interfaces since "ows_*" metadata can be used almost everywhere
  for common metadata items shared by multiple OGC interfaces.

.. index:: 
   triple: WFS; WEB; METADATA

Web Object Metadata
-------------------

.. index:: 
   triple: WFS; METADATA; ows_schemas_location

**ows_schemas_location**
  (Optional) (Note the name ows_schemas_location and not wfs/_...
  this is because all OGC Web Services (OWS) use the same metadata)
  Root of the web tree where the family of OGC WFS XMLSchema files are
  located. This must be a valid URL where the actual .xsd files are
  located if you want your WFS output to validate in a validating XML
  parser. Default is http://schemas.opengis.net.  See
  http://ogc.dmsolutions.ca for an example of a valid schema tree.

.. index:: 
   triple: WFS; METADATA; ows_updatesequence

**ows_updatesequence**
  (Optional) The updateSequence parameter can be used for maintaining
  the consistency of a client cache of the contents of a service
  metadata document. The parameter value can be an integer, a
  timestamp in [ISO 8601:2000] format, or any other number or string.

.. index:: 
   triple: WFS; METADATA; wfs_abstract

**wfs_abstract**
  (Optional) Descriptive narrative for more information about the
  server.

  WFS TAG Name: Abstract (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; METADATA; wfs_accessconstraints

**wfs_accessconstraints**
  (Optional) Text describing any access constraints imposed by the
  service provider on the WFS or data retrieved from this service.

  WFS TAG Name: Accessconstraints (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; METADATA; wfs_anable_request

**wfs_enable_request** (or **ows_enable_request**)
  Space separated list of requests to enable.  The default is none.
  The following requests can be enabled: `GetCapabilities`,
  `GetFeature` and `DescribeFeatureType`.  A "!" in front of a request
  will disable the request.  "*" enables all requests.

  *Examples:*

  To enable only `GetCapabilities` and `GetFeature`:

  ::

    "wfs_enable_request" "GetCapabilities GetFeature"

  To enable all requests except `GetCapabilities`

  ::

    "wfs_enable_request" "* !GetCapabilities"

.. index:: 
   triple: WFS; METADATA; wfs_encoding

**wfs_encoding**
  (Optional) XML encoding for all XML documents returned by the
  server. The default is ISO-8859-1.

.. index:: 
   triple: WFS; METADATA; wfs_feature_collection

**wfs_feature_collection**
  Replaces the default name of the feature-containing element
  (<msFeatureCollection>) with a user-defined value.

.. index:: 
   triple: WFS; METADATA; wfs_fees

**wfs_fees**
  (Optional) Any fees imposed by the service provider for usage of
  this service or for data retrieved from the WFS.

  WFS TAG Name: Fees (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; METADATA; wfs_getcapabilities_version

**wfs_getcapabilities_version**
  (Optional) Default version to use for GetCapabilities requests that
  do not have a version parameter.  If not set, the latest supported
  version will be returned.

.. index:: 
   triple: WFS; METADATA; wfs_keywordlist

**wfs_keywordlist**
  (Optional) List of words to aid catalog searching. 

  WFS TAG Name: Keyword (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; METADATA; wfs_maxfeatures

**wfs_maxfeatures**
  (Optional) The number of elements to be returned by the WFS server.
  This has priority over the 'maxfeatures' parameter passed by the
  user. If the not set the current behaviour is not changed.  Sensible
  values are integers greater than 0.  If 0 is specified, no features
  will be returned.

.. index:: 
   triple: WFS; METADATA; wfs_namespace_prefix

**wfs_namespace_prefix**
  (Optional) User defined namespace prefix to be used in the response
  of a WFS GetFeature request.  E.g.  "wfs_namespace_prefix"
  "someprefix".

.. index:: 
   triple: WFS; METADATA; wfs_namespace_uri

**wfs_namespace_uri**
  (Optional) User defined namespace URI to be used in the response of
  a WFS GetFeature request. e.g. "wfs_namespace_uri"
  "http://somehost/someurl".

.. index:: 
   triple: WFS; METADATA; wfs_onlineresource

**wfs_onlineresource**
  (Recommended) The URL prefix for HTTP GET requests.

  WFS TAG Name: Onlineresource (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; METADATA; wfs_service_onlineresource

**wfs_service_onlineresource**
  (Optional) Top-level onlineresource URL. MapServer uses the
  onlineresource metadata (if provided) in the following order:
         
  1. wfs_service_onlineresource

  2. ows_service_onlineresource

  3. wfs_onlineresource (or automatically generated URL, see the
     onlineresource section of this document)

.. index:: 
   triple: WFS; METADATA; wfs_srs

**wfs_srs**
  (Recommended) The SRS to use for all layers in this server.
  (e.g. EPSG:4326) See the note about the SRS rules in WFS.

.. index:: 
   triple: WFS; METADATA; wfs_title

**wfs_title**
  (Required) Human readable title to identify server. 

  WFS TAG Name: Title (WFS 1.0.0, sect. 12.3.3)

.. index:: 
   triple: WFS; LAYER; METADATA

Layer Object
------------

.. index:: 
   triple: WFS; METADATA; gml_constants

**gml_constants**
  (Optional) A comma delimited list of constants.  This option allows
  you to define data that are not part of the underlying dataset and
  add them to the GML output.  Many application schemas require
  constants of one form or another.  To specify the value and type of
  the constants use gml_[item name]_value and gml_[item name]_type.

  ::
  
    "gml_constants" "const1,const2"
    "gml_const1_type" "Character"
    "gml_const1_value" "abc"
    "gml_const2_type" "Integer"
    "gml_const2_value" "999"

.. index:: 
   triple: WFS; METADATA; gml_exclude_items

**gml_exclude_items**
  (Optional) A comma delimited list of items to exclude.  As of
  MapServer 4.6, you can control how many attributes (fields) you
  expose for your data layer with metadata. The previous behaviour was
  simply to expose all attributes all of the time. The default is to
  expose no attributes at all.  An example excluding a specific field
  would be:
  
  ::
  
    "gml_include_items" "all"
    "gml_exclude_items" "Phonenum"

.. index:: 
   triple: WFS; METADATA; gml_featureid

**gml_featureid**
  (Required for MapServer 4.10) Field to be used for the ID of the
  feature in the output GML.  wfs_featureid or ows_featureid can be
  specified instead.

.. index:: 
   triple: WFS; METADATA; gml_geometries

**gml_geometries**
  Provides a name other than the default "msGeometry" for geometry
  elements. The value is specified as a string to be used for geometry
  element names.

.. index:: 
   triple: WFS; METADATA; gml_[geometry name]_occurances

**gml_[geometry name]_occurances**
  MapServer applies default values of 0 and 1, respectively, to the
  "minOccurs" and "maxOccurs" attributes of geometry elements, as can
  be seen in the preceding examples. To override these defaults, a
  value is assigned to a gml_[geometry name]_occurances layer metadata
  item, where again [geometry name] is the string value specified for
  gml_geometries, and the value is a comma-delimited pair containing
  the respective lower and upper bounds.

.. index:: 
   triple: WFS; METADATA; gml_[geometry name]_type

**gml_[geometry name]_type**
  When employing gml_geometries, it is also necessary to specify the
  geometry type of the layer. This is accomplished by providing a
  value for gml_[geometry name]_type, where [geometry name] is the
  string value specified for gml_geometries, and a value which is one
  of:

  * point
  * multipoint
  * line
  * multiline
  * polygon
  * multipolygon

.. index:: 
   triple: WFS; METADATA; gml_groups

**gml_groups**
  (Optional) A comma delimited list of group names for the layer.

.. index:: 
   triple: WFS; METADATA; gml_[group name]_group

**gml_[group name]_group**
  (Optional) A comma delimited list of attributes in the group.  Here
  is an example:
  
  ::
  
    "gml_include_items" "all"
    "gml_groups"        "display"
    "gml_display_group" "Name_e,Name_f"

.. index:: 
   triple: WFS; METADATA; gml_include_items

**gml_include_items**
  (Optional) A comma delimited list of items to include, or keyword
  "all". As of MapServer 4.6, you can control how many attributes
  (fields) you expose for your data layer with this metadata. The
  previous behaviour was simply to expose all attributes all of the
  time. You can enable full exposure by using the keyword "all", such
  as:
  
  ::
  
    "gml_include_items" "all"
    
  You can specify a list of attributes (fields) for partial exposure,
  such as:
  
  ::
  
    "gml_include_items" "Name,ID"
    
  The new default behaviour is to expose no attributes at all.

.. index:: 
   triple: WFS; METADATA; gml_[item name]_alias

**gml_[item name]_alias**
  (Optional) An alias for an attribute's name.  The served GML will
  refer to this attribute by the alias.  Here is an example:

  ::
  
    "gml_province_alias" "prov"
    
.. index:: 
   triple: WFS; METADATA; gml_[item name]_precision

**gml_[item name]_precision**
  (Optional) Specifies the precision of the indicated field for
  formats where this is significant, such as Shapefiles.  Precision is
  the number of decimal places, and is only needed for "Real" fields.
  Currently this is only used for OGR based output formats, not the
  WFS GML2/GML3 output.

.. index:: 
   triple: WFS; METADATA; gml_[item name]_type

**gml_[item name]_type**
  (Optional) Specifies the type of the attribute.  Valid values are
  Integer|Real|Character|Date|Boolean.

.. index:: 
   triple: WFS; METADATA; gml_[item name]_value

**gml_[item name]_value**
  Used to specify values for gml_constants.

.. index:: 
   triple: WFS; METADATA; gml_[item name]_width

**gml_[item name]_width**
  (Optional) Specifies the width of the indicated field for formats
  where this is significant, such as Shapefiles.

.. index:: 
   triple: WFS; METADATA; gml_types

**gml_types**
  (Optional) If this field is "auto" then some input feature drivers
  (ie.  OGR, POSTGIS, ORACLESPATIAL and native shapefiles) will
  automatically populate the type, width and precision metadata for
  the layer based on the source file. Currently this is only used for
  OGR based output formats, not the WFS GML2/GML3 output.

  ::

    "gml_types"   "auto"

.. index:: 
   triple: WFS; METADATA; gml_xml_items

**gml_xml_items**
  (Optional) A comma delimited list of items that should not be
  XML-encoded.

.. index:: 
   triple: WFS; METADATA; wfs_abstract

**wfs_abstract**
  Same as wfs_abstract in the Web Object. 

.. index:: 
   triple: WFS; METADATA; wfs_anable_request

**wfs_enable_request** (or **ows_enable_request**)
  Space separated list of requests to enable.  The default is none.
  The following requests can be enabled: `GetCapabilities`,
  `GetFeature` and `DescribeFeatureType`.  A "!" in front of a request
  will disable the request.  "*" enables all requests.

  *Examples:*

  To enable only `GetCapabilities` and `GetFeature`:

  ::

    "wfs_enable_request" "GetCapabilities GetFeature"

  To enable all requests except `GetCapabilities`

  ::

    "wfs_enable_request" "* !GetCapabilities"

.. index:: 
   triple: WFS; METADATA; wfs_extent

**wfs_extent**
  (Optional) Used for the layer's BoundingBox tag for cases where it
  is impossible (or very inefficient) for MapServer to probe the data
  source to figure its extents. The value for this metadata is "minx
  miny maxx maxy" separated by spaces, with the values in the layer's
  projection units. If wfs_extent is provided then it has priority and
  MapServer will NOT try to read the source file's extents.

.. index:: 
   triple: WFS; METADATA; wfs_featureid

**wfs_featureid**
  (Required for MapServer 4.10) Field to be used for the ID of the
  feature in the output GML.  gml_featureid or ows_featureid can be
  specified instead.

.. index:: 
   triple: WFS; METADATA; wfs_getfeature_formatlist

**wfs_getfeature_formatlist**
  (Optional) Comma-separted list of formats that sould be valid for a
  GetFeature request.  If defined, only these formats are advertised
  through in the Capabilities document.

.. index:: 
   triple: WFS; METADATA; wfs_keywordlist

**wfs_keywordlist**
  Same as wfs_keywordlist in the Web Object. 

.. index:: 
   triple: WFS; METADATA; wfs_metadataurl_format

**wfs_metadataurl_format**
  (Optional) The file format of the metadata record. Valid values are
  "XML", "SGML", or "HTML". The layer metadata wfs_metadataurl_type
  and wfs_metadataurl_href must also be specified.  Refer to section
  12.3.5 of the `WFS 1.0.0 spec`_.

.. index:: 
   triple: WFS; METADATA; wfs_metadataurl_href

**wfs_metadataurl_href**
  (Optional) The URL to the layer's metadata. The layer metadata
  wfs_metadataurl_type and wfs_metadataurl_format must also be
  specified.  Refer to section 12.3.5 of the `WFS 1.0.0 spec`_.

.. index:: 
   triple: WFS; METADATA; wfs_metadataurl_type

**wfs_metadataurl_type**
  (Optional) The standard to which the metadata complies. Currently
  only two types are valid: "TC211" which refers to [ISO 19115], and
  "FGDC" which refers to [FGDC CSDGM]. The layer metadata
  wfs_metadataurl_format and wfs_metadataurl_href must also be
  specified.  Refer to section 12.3.5 of the `WFS 1.0.0 spec`_.

.. index:: 
   triple: WFS; METADATA; wfs_srs

**wfs_srs**
  If there is no SRS defined at the top-level in the mapfile then this
  SRS will be used to advertize this feature type (layer) in the
  capabilities. See the note about the SRS rules in WFS.

.. index:: 
   triple: WFS; METADATA; wfs_title

**wfs_title**
  Same as wfs_title in the Web Object. 

To-do Items and Known Limitations
==================================

- This is just a basic WFS (read-only): transaction requests are not
  supported and probably never will given the nature of MapServer.
  `GeoServer`_ or `TinyOWS`_ is recommended for those needing WFS-T
  support.

- WFS spec. seems to require that features of a given feature type
  must all be of the same geometry type (point, line, polygon). This
  works fine for shapefiles, but some data source formats supported by
  MapServer allow mixed geometry types in a single layer and this goes
  against the WFS spec. Suggestions on how to handle this are welcome
  (send suggestions to the :ref:`mapserver-dev mailing list <lists>`.

.. #### rST Link Section ####

.. _`OGC Web Feature Service Implementation Specification`: https://portal.opengeospatial.org/files/?artifact_id=7176
.. _`Geography Markup Language Implementation Specification`: https://portal.opengeospatial.org/files/?artifact_id=7174
.. _`OGC Web Services Workshop package`: http://ms-ogc-workshop.maptools.org/
.. _`MS4W`: http://www.maptools.org/ms4w/
.. _`WFS 1.0.0 specification`: https://portal.opengeospatial.org/files/?artifact_id=7176
.. _`Quantum GIS`: http://www.qgis.org/
.. _`Deegree`: http://www.deegree.org/
.. _`owsview`: http://devgeo.cciw.ca/owsview
.. _`uDig`: http://udig.refractions.net/
.. _`WFS 1.0.0 spec`: https://portal.opengeospatial.org/files/?artifact_id=7176
.. _`GeoServer`: http://geoserver.org
.. _`TinyOWS`: http://www.tinyows.org
.. _`GML2 request output`: http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=getfeature&TYPENAME=continents&MAXFEATURES=1&OUTPUTFORMAT=gml2
.. _`GML3 request output`: http://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=1.0.0&REQUEST=getfeature&TYPENAME=continents&MAXFEATURES=1&OUTPUTFORMAT=gml3
.. _`bug#884`: http://trac.osgeo.org/mapserver/ticket/884