1.1   WFS-Related Information

Although in-depth understanding of WFS and GML is neither necessary nor required in order to implement a MapServer application that reads remote WFS data, it is recommended to at least get aquainted with the concepts and basic functionality of both. Here are the official references (including a newly added OGC workshop with MapServer):

• OGC Web Feature Service Implementation Specification.
• Geography Markup Language Implementation Specification.
• MapServer OGC Web Services Workshop package.

1.2   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 librairies. Version 1.1.8 or greater is required.
• LibCURL: Used to help MapServer act as an HTTP client. Version 7.10 or greater is required.

Please see the MapServer UNIX Compilation and Installation HOWTO for detailed instructions on compiling mapserver with support for these librairies and features. For Windows users, look on the MapServer website to see if there are any binaries available that meet these requirements.

2.1   Storing Temporary Files

You must set the IMAGEPATH parameter in your mapfile since MapServer uses this directory to store temporary files downloaded from the remote WFS server.

MAP
  ...
  WEB
    IMAGEPATH "/tmp/ms_tmp/"
    IMAGEURL ...
  END
  ...
END 

2.2   WFS Layer

A WFS layer is a regular mapfile layer, which can use CLASS objects, with expressions, etc.

As of MapServer 4.4, the suggested method to define a WFS Client layer is through the CONNECTION parameter and the layer's METADATA. The necessary mapfile parameters are defined below:

• CONNECTIONTYPE: must be "wfs"

• CONNECTION: The URL to the WFS Server. e.g. http://www2.dmsolutions.ca/cgi-bin/mswfs_gmap? The path to the mapfile on the WFS server is required if it was required in the GetCapabilities request e.g. you would have to specify the MAP parameter in the CONNECTION for the following server: http://map.ns.ec.gc.ca/MapServer/mapserv.exe?MAP=/mapserver/services/envdat/config.map &SERVICE=WFS&VERSION=1.0.0&REQUEST=GetCapabilities

• METADATA: The LAYER's must contain a METADATA object with the following parameters:

  • wfs_connectiontimeout (optional): The maximum time to wait for a remote WFS layer to load, set in seconds (default is 30 seconds). This metadata can be added at the layer level so that it affects only that layer, or it can be added at the map level (in the web object) so that it affects all of the layers. Note that wfs_connectiontimeout at the layer level has priority over the map level.

  • wfs_filter: This can be included to include a filter encoding parameter in the getFeature request (see the Filter Encoding HOWTO for more information on filtering). The content of the wfs_filter is a valid filter encoding element.

    ...
    METADATA
      "wfs_filter"   "<PropertyIsGreaterThan><PropertyName>POP_RANGE</PropertyName><Literal>4
                      </Literal></PropertyIsGreaterThan>"
    END
    ...
    

  • wfs_latlongboundingbox (optional): The bounding box of this layer in geographic coordinates in the format "lon_min lat_min lon_max lat_max". If it is set then MapServer will request the layer only when the map view overlaps that bounding box. You normally get this from the server's capabilities output.

  • wfs_maxfeatures (optional): Limit the number of GML features to return.

  • wfs_request_method (optional): Can be set to "GET" to do a Get request to WFS servers that do not support Post requests. The default method in MapServer is Post.

    ...
    METADATA
      "wfs_filter"   "GET"
    END
    ...
    

  • wfs_typename (required): the <Name> of the layer found in the GetCapabilities. An example GetCapabilities request is: http://www2.dmsolutions.ca/cgi-bin/mswfs_gmap?SERVICE=WFS&VERSION=1.0.0&REQUEST=getcapabilities

  • wfs_version (required): WFS version, currently "1.0.0"

2.3   Example WFS Layer

LAYER
  NAME park
  TYPE POLYGON
  STATUS ON
  CONNECTIONTYPE WFS
  CONNECTION "http://www2.dmsolutions.ca/cgi-bin/mswfs_gmap?"
  METADATA
    "wfs_typename"          "park"
    "wfs_version"           "1.0.0"
    "wfs_request_method"    "GET"
    "wfs_connectiontimeout" "60"
    "wfs_maxfeatures"       "1"
  END
  PROJECTION
    "init=epsg:42304"
  END
  CLASS
    NAME "Parks"
    STYLE
      COLOR 200 255 0
      OUTLINECOLOR 120 120 120
    END
  END
END # Layer

2.4   Connection - deprecated

As of MapServer v4.4 the method of specifying all of the connection information in the CONNECTION parameter has beendeprecated. The preferred method is mentioned above. If the metadata is not provided, VERSION, SERVICE, and TYPENAME will be fetched from the CONNECTION, as shown below:

CONNECTION    "http://www2.dmsolutions.ca/cgi-bin/mswfs_gmap?SERVICE=WFS&VERSION=1.0.0&TYPENAME=park"

4.1   Copyright Information

Copyright (c) 2005, Jean-François Doyon, Jeff McKenna.

This documentation is covered by the same Open Source license as the MapServer software itself. See MapServer's License and Credits page for the complete text.

4.2   Disclaimer

No liability for the contents of this document can be accepted. Use the concepts, examples and other content at your own risk. As this is a new edition of this document, there may be errors and inaccuracies that may be damaging to your system. Although this is highly unlikely, the author(s) do not take any responsibility for that: proceed with caution.