WFS Server

Author:

Jeff McKenna

Contact:

jmckenna at gatewaygeomatics.com

Author:

Even Rouault

Contact:

even.rouault at mines-paris.org

Last Updated:

2024-07-08

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.

In version 7.0, MapServer supports versions 1.0, 1.1 and 2.0 of the WFS specifications.

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.

For WFS 2.0, the following documents apply :

• The OGC WFS 2.0 specification.

• The OGC Filter Encoding 2.0 specification.

• The OGC GML 3.2.1 specification.

Technical details on the implementation of WFS 2.0 in MapServer are given in the MS RFC 105: Support for WFS 2.0 (server side).

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 libraries:

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

• GDAL/OGR: I/O support libraries. Version 1.6.0 or greater is required.

Please see the MapServer UNIX Compilation and Installation HowTo 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.

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

With WFS 2.0, the default OUTPUTFORMAT is "application/gml+xml; version=3.2".

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

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 WMS Server document.

  ملاحظة

  It is strongly recommended to review the security steps for the MAP= call to the MapServer executable, by setting MS_MAP_PATTERN or MS_MAP_NO_PATH or hiding the MAP= parameter on public servers, as recommended in the document Limit Mapfile Access. All possible environment variables to secure your server are listed in Environment Variables.

• 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.

MAP
  NAME "WFS_server" ##strongly recommended. containing no special characters or spaces
  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" "https://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
      "gml_types"         "auto" ## Optional (automatically populate the type for the attributes)
      "wfs_enable_request" "*"
      "wfs_use_default_extent_for_getfeature" "false" ## Optional (improves performance of OGR layers)
    END
    TYPE POLYGON
    STATUS ON
    DATA "shapefile/countries_area"
    # define source projection
    PROJECTION
      "init=epsg:4326"
    END
    CLASS
      NAME "World Continents"
      STYLE
        COLOR 255 128 128
        OUTLINECOLOR 96 96 96
      END
    END
  END #layer

END #mapfile

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 and 2.0 specifications allow 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.

ملاحظة

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.

ملاحظة

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

ملاحظة

The first advertised wfs_srs / ows_srs metadata value will be used as the default projection of the bbox requested (unless explicitly set) and will be using in spatial filtering the data for those layer types that support spatial filtering. If the data is in a different projection, the spatial filter BBOX will be projected to match the source data.

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 and 2.0

The axis order in previous versions of the WFS specifications was to always use easting (x or lon ) and northing (y or lat). WFS 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.

Regarding SRS, for WFS 2.0, it will always be reported with the "urn:ogc:def:crs:EPSG::" syntax. This should likely also be done for WFS 1.1.0. The "wfs_return_srs_as_urn" web metadata item can be set to "true" or "false" to enable or disable this behaviour. It defaults to "true" for WFS 2.0 and to "false" for older versions.

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.

https://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.

ملاحظة

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.

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

For WFS 2.0, the same request would be :

https://demo.mapserver.org/cgi-bin/wfs?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=continents&COUNT=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 WFS Client HowTo.

• QGIS is a full GIS package which includes WFS client support. (recommended)

• Deegree provides a WFS client.

• uDig can add layers from WMS/WFS servers.

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 Filter Encoding HowTo.

Support for Sorting

Sorting is supported for WFS 1.1 and 2.0. WFS clients can add a SORTBY parameter to the query string to order results based on one or more attribute values e.g. SORTBY=Field1 DESC,Field2 ASC.

The list of drivers that support sorting (sorting was implemented in MapServer 7.0 unless otherwise specified):

• OGR

• PostGIS

• Oracle

• MS SQL Server (version 7.4)

The MapServer Shapefile provider does not support sorting. If this needed, you must use the OGR Shapefile provider.

Further sorting implementation details can be found in MS RFC 105: Support for WFS 2.0 (server side).

MapServer WFS Extensions

STARTINDEX

This is standard in WFS 2.0, and also available as a MapServer extension for WFS 1.0 and 1.1. In addition to the MAXFEATURES=n keyword (replaced by COUNT in WFS 2.0), 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 (or COUNT) provides for the ability to use WFS GetFeature to page through results. Note that STARTINDEX=0 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. For WFS 2.0, the default is "application/gml+xml; version=3.2", but GML2 and GML3 can also be requested. 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 OGR Output document.

Stored queries (WFS 2.0)

Stored queries are queries (<wfs:Query>) stored on the server, potentially with parameters whose value can be assigned by the client during a GetFeature request.

At WEB.METADATA level, a "wfs_storedqueries" metadata item can be specified with a comma separated list of stored queries ids.

Then for each stored query id, "wfs_[storedqueryid]_inlinedef" must be specified with a valid <StoredQueryDescription> as value. As it is not always convenient to specify a inline XML content, it is also possible to specify "wfs_{storedqueryid}_filedef" whose value is a filename that contains the <StoredQueryDescription> XML content.

"wfs_storedqueries"           "bboxstoredquery"
"wfs_bboxstoredquery_filedef" "/data/bboxstoredquery.xml"

with /data/bboxstoredquery.xml containing for example:

<?xml version="1.0" encoding="UTF-8"?>
<StoredQueryDescription xmlns:xs="http://www.w3.org/2001/XMLSchema"
                        xmlns:gml="http://www.opengis.net/gml/3.2"
                        id="bboxstoredquery">
    <Title>query title</Title>
    <Abstract>query abstract</Abstract>
    <Parameter name="longmin" type="xs:double"/>
    <Parameter name="latmin" type="xs:double"/>
    <Parameter name="longmax" type="xs:double"/>
    <Parameter name="latmax" type="xs:double"/>
    <QueryExpressionText isPrivate="false"
                        language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression"
                        xmlns:ms="http://mapserver.gis.umn.edu/mapserver"
                        returnFeatureTypes="ms:firstLayer ms:secondLayer">
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="ms:firstLayer">
            <fes:Filter>
                <fes:BBOX>
                    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
                        <gml:lowerCorner>${latmin} ${longmin}</gml:lowerCorner>
                        <gml:upperCorner>${latmax} ${longmax}</gml:upperCorner>
                    </gml:Envelope>
                </fes:BBOX>
            </fes:Filter>
        </Query>
        <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="ms:secondLayer">
            <fes:Filter>
                <fes:BBOX>
                    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
                        <gml:lowerCorner>${latmin} ${longmin}</gml:lowerCorner>
                        <gml:upperCorner>${latmax} ${longmax}</gml:upperCorner>
                    </gml:Envelope>
                </fes:BBOX>
            </fes:Filter>
        </Query>
    </QueryExpressionText>
</StoredQueryDescription>

A corresponding valid GetFeature request can be:

REQUEST=GetFeature&STOREDQUERY_ID=bboxstoredquery&LONGMIN=2&LATMIN=49&LONGMAX=3&LATMAX=50

Predefined urn:ogc:def:query:OGC-WFS::GetFeatureById stored query

WFS 2.0 defines a mandatory "urn:ogc:def:query:OGC-WFS::GetFeatureById" stored query. This query accept a ID parameter whose value must be a feature id.

A valid request is: REQUEST=GetFeature&STOREDQUERY_ID=urn:ogc:def:query:OGC-WFS::GetFeatureById&ID=mylayer.3

The definition hardcoded in MapServer is:

<?xml version="1.0" encoding="UTF-8"?>
<StoredQueryDescription id="urn:ogc:def:query:OGC-WFS::GetFeatureById">
  <Title>Get feature by identifier</Title>
  <Abstract>Returns the single feature whose value is equal to the specified value of the ID argument</Abstract>
  <Parameter name="ID" xmlns:xs="http://www.w3.org/2001/XMLSchema" type="xs:string"/>
  <QueryExpressionText isPrivate="true"
        language="urn:ogc:def:queryLanguage:OGC-WFS::WFS_QueryExpression"
        returnFeatureTypes="">
    <Query xmlns:fes="http://www.opengis.net/fes/2.0" typeNames="?">
      <fes:Filter>
        <fes:ResourceId rid="${ID}"/>
      </fes:Filter>
    </Query>
  </QueryExpressionText>
</StoredQueryDescription>

Comparing to a more standard stored query description, there are 2 oddities : The value of the "returnFeatureTypes" attribute is replaced at runtime by the name of the valid WFS layers of the mapfile (when issuing the response document to DescribeStoredQueries request). And the value of the typeNames attribute is deduced at runtime from the value of the passed ID parameter.

It is possible to override this hardcoded definition by a custom one (for example to provide alternate values for other languages) by defining "wfs_urn:ogc:def:query:OGC-WFS::GetFeatureById_inlinedef" or "wfs_urn:ogc:def:query:OGC-WFS::GetFeatureById_filedef". The value of <QueryExpressionText> attributes and child elements must however be strictly identical to the hard-coded definition for correct execution.

A GetFeature using "urn:ogc:def:query:OGC-WFS::GetFeatureById" seems to be identical to a GetFeature with a RESOURCEID parameter, but there is a difference. GetFeatureById returns the feature directly as the response :

<?xml version='1.0' encoding="UTF-8" ?>
<ms:province gml:id="province.977" xmlns:ms="http://mapserver.gis.umn.edu/mapserver"
    xmlns:gml="http://www.opengis.net/gml/3.2"
    xmlns:wfs="http://www.opengis.net/wfs/2.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://mapserver.gis.umn.edu/mapserver
      http://localhost/path/to/wfs_simple?myparam=something&amp;
        SERVICE=WFS&amp;VERSION=2.0.0&amp;REQUEST=DescribeFeatureType&amp;
        TYPENAME=province&amp;
        OUTPUTFORMAT=application%2Fgml%2Bxml%3B%20version%3D3.2
      http://www.opengis.net/wfs/2.0
      http://schemas.opengis.net/wfs/2.0/wfs.xsd
      http://www.opengis.net/gml/3.2
      http://schemas.opengis.net/gml/3.2.1/gml.xsd">
<gml:boundedBy>
  <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
  <gml:lowerCorner>47.76789 -61.51051</gml:lowerCorner>
  <gml:upperCorner>47.79644 -61.45764</gml:upperCorner>
  </gml:Envelope>
</gml:boundedBy>
<ms:msGeometry>
  <gml:Polygon gml:id="province.977.1" srsName="urn:ogc:def:crs:EPSG::4326">
    <gml:exterior>
      <gml:LinearRing>
      <gml:posList srsDimension="2">47.77424 -61.51051 47.78860 -61.50894
        47.79644 -61.49272 47.78743 -61.45764 47.76789 -61.45998 47.76961
        -61.48350 47.77424 -61.51051 </gml:posList>
      </gml:LinearRing>
    </gml:exterior>
  </gml:Polygon>
</ms:msGeometry>
</ms:province>

Reference Section

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

ملاحظة

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.

Web Object Metadata

ows_allowed_ip_list (or wfs_allowed_ip_list)

• Description: (Optional) A list of IP addresses that will be allowed access to the service.

  Example:

  METADATA
    "ows_allowed_ip_list" "123.45.67.89 11.22.33.44"
  END
  

ows_denied_ip_list (or wfs_denied_ip_list)

• Description: (Optional) A list of IP addresses that will be denied access to the service.

  Example:

  METADATA
    "ows_denied_ip_list" "123.45.67.89 11.22.33.44"
  END
  

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.

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.

wfs_abstract

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

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

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)

wfs_compute_number_matched

(Optional, WFS 2.0 only) When this metadata item is set to "true", the server will determine the number of features that match the GetFeature request and return it in the 'numberMatched' attribute of the <FeatureCollection> element in the response. Computing that number might take a very long time, so it is strongly encouraged to NOT define this item. When it is not defined, the 'numberMatched' attribute is set to "unknown".

See "wfs_maxfeatures_ignore_for_resulttype_hits" for a similar setting affecting resultType=hits GetFeature 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"

wfs_feature_collection

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

wfs_features_cache_count

(Optional, since MapServer 7.2) Maximum number of features retrieved during the first query pass that should be cached, so as not to be asked again to the datasource. This might be set to the same value as wfs_maxfeatures, but not necessarily. If wfs_features_cache_size is also set, the most limiting will be honoured. Note: this is an advanced setting.

wfs_features_cache_size

(Optional, since MapServer 7.2) Maximum amount of RAM allowed to cache features during the first query pass, so as not to be asked again to the datasource when geneating the GML or OGR output. If wfs_features_cache_count is also set, the most limiting will be honoured. By default the value is in bytes, unless the " MB" suffix is specified. Note: this is an advanced setting.

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)

wfs_geometry_precision

(Optional, since MapServer 8.0) Specifies the precision of the geometry coordinates in the generated GML, where precision is the number of decimal places. This affects WFS requests using the built-in GML2/GML3 output (specifying a different OUTPUTFORMAT will override this setting).

ملاحظة

setting wfs_geometry_precision at the LAYER-level will override any value set here in the WEB metadata.

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. As of MapServer 7.0, this default version is "2.0.0". Valid values are "1.0.0", "1.1.0" and "2.0.0".

wfs_keywordlist

(Optional) List of words to aid catalog searching.

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

wfs_languages

• Description: (Optional) A comma-separated list of supported languages. For details please refer to the section Multi-language support for certain capabilities fields in the INSPIRE Download Service documentation.

wfs_maxfeatures

(Optional) The maximum and default number of elements to be returned by the WFS server. If the user sets the 'maxfeatures' parameter in a GetFeatureRequest, his value will be used, provided it does not exceed wfs_maxfeatures. If wfs_maxfeatures is not specified, the server will return all the features that match the query, without limit, which may make the server busy for a long time when layers with big number of features are served. Sensible values are integers greater than 0. If 0 is specified, no features will be returned. In WFS 2.0, this item is used to fill the "CountDefault" parameter of the response document to a GetCapabilities request, so that clients are aware of the server limit. See also the "wfs_maxfeatures_ignore_for_resulttype_hits" item.

wfs_maxfeatures_ignore_for_resulttype_hits

(Optional, added in MapServer 7.2) Controls whether the limit set by "wfs_maxfeatures" is also taken into account in resultType=hits GetFeature requests.

See "resultType parameter" chapter (OGC WFS 2.0 specification, sect. 7.6.3.6)

When setting this item to "false", the limit set by "wfs_maxfeatures" will also be taken into account when processing a resultType=hits GetFeature request, that is to say the number of hits returned will not be greater than wfs_maxfeatures. This is the behaviour in MapServer version prior to 7.2, and also the general default behaviour in later versions. Unless if all the layers that are queried are PostGIS layers, in which case wfs_maxfeatures is not taken into account when computing the number of hits. The item may be explicitly set to "true" so that wfs_maxfeatures is not taken into account when computing the number of hits (for any layer type), which may exhibit performance issues for large layers and/ or backends with slow access.

This item has no effect if wfs_maxfeatures is not set.

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".

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".

wfs_onlineresource

(Recommended) The URL prefix for HTTP GET requests.

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

wfs_return_srs_as_urn

(Optional) Defaults to "true" in WFS 2.0, and "false" in WFS 1.0 and 1.1. When set to "true", SRS in GetFeature response documents will always be reported with the "urn:ogc:def:crs:EPSG::" syntax.

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)

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.

wfs_storedqueries

(Optional, WFS 2.0) A comma separated list of stored queries IDs. The definition of each of those stored queries must be given with wfs_[storedqueryid]_inlinedef or wfs_[storedqueryid]_filedef

wfs_[storedqueryid]_inlinedef

(Optional, WFS 2.0) Inline XML content for a stored query listed in wfs_storedqueries. This content must be a valid <StoredQueryDescription> document.

wfs_[storedqueryid]_filedef

(Optional, WFS 2.0) Name of a file that contains a valid <StoredQueryDescription> document.

wfs_title

(Required) Human readable title to identify server. WFS TAG Name: Title (WFS 1.0.0, sect. 12.3.3)

Layer Object

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"

gml_default_items

(Optional) A comma delimited list of items to put in a GetFeature response document without explicit PROPERTYNAME, or "all". When a GetFeature request without explicit PROPERTYNAME is processed, MapServer returns all items by default. As of MapServer 7.0, this behaviour can be amended by specifying "gml_default_items" to specify which items (among the optional ones) must be returned.

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"

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.

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. "none" will exclude the geometry from MapServer integrated output (OGR outputformat doesn't honour this setting).

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.

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

ows/wfs_geomtype

(Optional, metadata shared with OGR output). Set the geometry type of OGR layers created from this MapServer LAYER. One of "Point", "LineString", "Polygon", "MultiPoint", "MultiLineString", "MultiPolygon", "GeometryCollection", "Geometry", or "None". Most are fairly obvious, but "Geometry" can be used to represent a mix of geometry types, and "None" is sometimes suitable for layers without geometry. Note that layers which are a mix of polygon and multipolygon would normally have to be described as "Geometry". To produce 2.5D output append "25D" to the geometry type (ie. "Polygon25D"). Note that Z values are only carried by MapServer if built with USE_POINT_Z_M support.

"ows_geomtype"  "Polygon25D"

ملاحظة

For GML output, only the "25D" suffix of the value is taken into account to determine whether Z coordinates should be output or not.

gml_groups

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

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"

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.

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"

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.

gml_[item name]_type (Optional)

Specifies the type of the attribute. Valid values are the OGR data types: Integer|Long|Real|Character|Date|Time|DateTime|Boolean. MapServer translates these to valid GML data types.

ملاحظة

Long is to be used for 64-bit integers, starting with MapServer 7.0.1.

ملاحظة

Time and DateTime have been added in MapServer 8. And since MapServer 8, Date semantics is a date, without time, whereas in previous versions, it was used indifferently for Date, Time or DateTime.

gml_[item name]_value

Used to specify values for gml_constants.

gml_[item name]_width

(Optional) Specifies the width of the indicated field for formats where this is significant, such as Shapefiles.

gml_mandatory_items

(Optional) A comma delimited list of items to make mandatory, or keyword "all". See gml_optional_items.

gml_optional_items

(Optional) A comma delimited list of items to make optional, or keyword "all". By default, as of MapServer 7.0, all items are considered as optional (minOccurs="0" in the GML application schema). If "gml_optional_items" is specified, only the listed elements will be optional and other included items will be mandatory. If there are more mandatory items, it might be more convenient to specify "gml_mandatory_items".

gml_types

(Optional) If this field is set to "auto" then the OGR, POSTGIS, ORACLESPATIAL, MSSQL, and native Shapefiles input feature drivers will automatically populate the type, width and precision metadata for the layer based on the source file. This is mainly used by OGR based output formats, as well as the WFS GML2/GML3 output to format dates.

In addition the MSSQL driver also sets nillable="true" in the output GML for any database fields that accept NULLs.

This option can be overridden by setting gml_[item name]_type for individual fields.

"gml_types"   "auto"

gml_xml_items

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

ows_allowed_ip_list

Same as ows_allowed_ip_list in the Web Object.

ows_denied_ip_list

Same as ows_denied_ip_list in the Web Object.

wfs_abstract

Same as wfs_abstract in the Web Object.

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"

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.

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.

wfs_geometry_precision

(Optional, since MapServer 8.0) Specifies the precision of the geometry coordinates in the generated GML, where precision is the number of decimal places. This affects WFS requests using the built-in GML2/GML3 output (specifying a different OUTPUTFORMAT will override this setting).

ملاحظة

setting wfs_geometry_precision here at the LAYER-level will override any value set in the WEB wfs_geometry_precision metadata.

wfs_getfeature_formatlist

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

wfs_keywordlist

Same as wfs_keywordlist in the Web Object.

wfs_metadataurl_about

• (Optional) used to reference the aspect of the element which includes the MetadataURL element that this metadata provides more information about. The layer metadata wfs_metadataurl_href must also be specified. Refer to Table 11 of the OGC WFS 2.0 specification (WFS 2.0 only)

• To output several MetadataURL elements, use wfs_metadataurl_list

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 (unused for WFS 2.0).

• To output several MetadataURL elements, use wfs_metadataurl_list

wfs_metadataurl_href

• (Optional) The URL to the layer's metadata. The layer metadata wfs_metadataurl_type and wfs_metadataurl_format for WFS 1.0 and 1.1, or wfs_metadataurl_about for WFS 2.0 may also be specified. Refer to section 12.3.5 of the WFS 1.0.0 spec and Table 11 of the OGC WFS 2.0 specification

• To output several MetadataURL elements, use wfs_metadataurl_list

wfs_metadataurl_list

Added in version 8.0.

• (Optional) Space-separated list of parts of metadata keys, to be able to specify several MetadataURL. If the value of wfs_metadataurl_list is "foo bar", then wfs_metadataurl_foo_href, wfs_metadataurl_foo_format, wfs_metadataurl_foo_type, wfs_metadataurl_foo_about, wfs_metadataurl_bar_href, wfs_metadataurl_bar_format, wfs_metadataurl_bar_type, wfs_metadataurl_bar_about will be queried with the semantics of the wfs_metadataurl_href, wfs_metadataurl_format, wfs_metadataurl_type and wfs_metadataurl_about items.

  Example:

  "wfs_metadataurl_list" "xml html"
  
  "wfs_metadataurl_xml_format" "text/xml"
  "wfs_metadataurl_xml_type" "TC211"
  "wfs_metadataurl_xml_href" "http://example.com/testXML"
  "wfs_metadataurl_xml_about" "about XML"
  
  "wfs_metadataurl_html_format" "text/html"
  "wfs_metadataurl_html_type" "TC211"
  "wfs_metadataurl_html_href" "http://example.com/testHTML"
  "wfs_metadataurl_html_about" "about HTML"
  

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 (unused for WFS 2.0).

• To output several MetadataURL elements, use wfs_metadataurl_list

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.

wfs_title

Same as wfs_title in the Web Object.

wfs_use_default_extent_for_getfeature

(Optional, since MapServer 7.0.4) Whether the MAP.EXTENT should be used in request to datasources in the absence of other spatial filter. This is the default behaviour, but this might affect performance in some use cases. In those cases, setting this item to "false" will avoid he default spatial filter to be appended to the request. This is only implemented for OGR datasources (since 7.0.4) and MSSQL2008 connections (since 7.6)

Layer Metadata API

If wfs_metadataurl_href is not defined, MapServer will provide a link to the Layer Metadata API for the given layer in the <MetadataURL> element. See the Layer Metadata API documentation for more information.

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 mapserver-dev mailing list.