1   Introduction

This document describes the procedures for taking advantage of the Filter Encoding (FE) support in WFS GetFeature requests, which was added to MapServer in version 4.2.

This document assumes that you are already familiar with the following aspects of MapServer:

• MapServer application development and setting up .map files.
• Familiarity with the WFS specification would be an asset. Links to the MapServer WFS documents are included in the next section.

2   Currently Supported Features

The following table lists the currently supported features for FE.

Table 1. Currently Supported Features

3   Get and Post Requests

MapServer already has the capability to receive and parse Get requests and URL-encoded Post requests. The ability for MapServer to be able to receive Post requests with XML-encoded information sent in the body of the request has been added. Also, the ability to generate XML-encoded Post requests for WFS layers has been added.

Both Get and Post request are now supported for all WFS requests:

• GetCapabilities
• GetFeatures
• DescribeFeatureType

Supporting these WFS requests in Post was implemented to keep consistency between all supported WFS requests.

When sending requests, the default request method used is Post. To change this behavior, we have introduced a layer level meta data, wfs_request_method, which can be set to "GET".

4   Use of Filter Encoding in MapServer

This section describes how to use FE on both the server and client sides.

<?xml version='1.0' encoding="ISO-8859-1" ?>
<WFS_Capabilities 
   version="1.0.0" 
   updateSequence="0" 
   xmlns="http://www.opengis.net/wfs" 
   xmlns:ogc="http://www.opengis.net/ogc" 
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.opengis.net/wfs http://ogc.dmsolutions.ca/wfs/1.0.0/WFS-capabilities.xsd">

<!-- MapServer version 4.1 OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP 
OUTPUT=PDF OUTPUT=SWF SUPPORTS=PROJ SUPPORTS=FREETYPE SUPPORTS=WMS_SERVER 
SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT INPUT=POSTGIS 
INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE -->

<Service>
  <Name>MapServer WFS</Name>
  <Title>GMap WMS Demo Server</Title>
  <OnlineResource>http://localhost/cgi-bin/mapserv.exe?map=
    c:/msapps/wfs_filter/htdocs/ns_wfsserver.map&</OnlineResource>
</Service>

<Capability>
  <Request>
    <GetCapabilities>
      <DCPType>
        <HTTP>
          <Get onlineResource="http://localhost/cgi-bin/mapserv.exe?map=
            c:/msapps/wfs_filter/htdocs/ns_wfsserver.map&" />
        </HTTP>
      </DCPType>
      <DCPType>
        <HTTP>
          <Post onlineResource="http://localhost/cgi-bin/mapserv.exe?map=
            c:/msapps/wfs_filter/htdocs/ns_wfsserver.map&" />
        </HTTP>
      </DCPType>
    </GetCapabilities>
    ...
  </Request>
</Capability>
...
<Filter_Capabilities>
  <Spatial_Capabilities>
    <Spatial_Operators>
             <Intersect/>
             <DWithin/>
           <BBOX/>
    </Spatial_Operators>
  </Spatial_Capabilities>
  <Scalar_Capabilities>
    <Logical_Operators />
    <Comparison_Operators>
      <Simple_Comparisons />
      <Like />
      <Between />
    </Comparison_Operators>
  </Scalar_Capabilities>
</Filter_Capabilities>

</WFS_Capabilities>

LAYER
  NAME popplace
  METADATA
    "wfs_version"   "1.0.0"       
    "wfs_typename"  "popplace"
    "wfs_filter"    "<PropertyIsGreaterThan><PropertyName>POP_RANGE</PropertyName>
                                     <Literal>4</Literal></PropertyIsGreaterThan>"        
  END
  TYPE POINT
  STATUS ON
  PROJECTION
    "init=epsg:42304"
  END
  CONNECTIONTYPE WFS
  CONNECTION "http://www2.dmsolutions.ca:8090/cgi-bin/mswfs_filter?"
  LabelItem "Name"  
  CLASSITEM "Capital" 
  CLASS
    SYMBOL 2
    SIZE 8
    NAME "Cities"
    LABEL
      COLOR  255 0 0
      FONT fritqat-italic
      TYPE truetype
      SIZE 8
      POSITION AUTO         
      OUTLINECOLOR 255 255 255  
      FORCE TRUE
    END 
    COLOR 0 0 0
  END
END # Layer

5   Limitations

• A limited set of spatial operators are supported.

6   Tests

Here are some test URLs for the different supported filters:

• PropertyIsEqualTo

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsEqualTo><PropertyName>NAME</PropertyName>
<Literal>Digby</Literal></PropertyIsEqualTo></Filter> 

• PropertyIsNotEqualTo

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsNotEqualTo><PropertyName>NAME</PropertyName>
<Literal>Digby</Literal></PropertyIsNotEqualTo></Filter>

• PropertyIsLessThan

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsLessThan><PropertyName>POP_RANGE</PropertyName>
<Literal>2</Literal></PropertyIsLessThan></Filter>

• PropertyIsGreaterThan

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsGreaterThan><PropertyName>POP_RANGE</PropertyName>
<Literal>5</Literal></PropertyIsGreaterThan></Filter>

• PropertyIsLessThanOrEqualTo

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsLessThanOrEqualTo><PropertyName>POP_RANGE</PropertyName>
<Literal>2</Literal></PropertyIsLessThanOrEqualTo></Filter>

• PropertyIsGreaterThanOrEqualTo

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsGreaterThanOrEqualTo><PropertyName>POP_RANGE</PropertyName>
<Literal>5</Literal></PropertyIsGreaterThanOrEqualTo></Filter>

• PropertyIsBetween

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsBetween><PropertyName>POP_RANGE</PropertyName>
<LowerBoundary>5</LowerBoundary><UpperBoundary>6</UpperBoundary></PropertyIsBetween></Filter>

• PropertyIsLike

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><PropertyIsLike wildcard='*' singleChar='.' escape='!'>
<PropertyName>NAME</PropertyName><Literal>Syd*</Literal></PropertyIsLike></Filter>

• Logical operator OR

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><OR><PropertyIsEqualTo><PropertyName>NAME</PropertyName>
<Literal>Sydney</Literal></PropertyIsEqualTo><PropertyIsEqualTo><PropertyName>NAME</PropertyName>
<Literal>Digby</Literal></PropertyIsEqualTo></OR></Filter>

• Logical operator AND

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><AND><PropertyIsLike wildcard='*' singleChar='.' escape='!'>
<PropertyName>NAME</PropertyName><Literal>Syd*</Literal></PropertyIsLike><PropertyIsEqualTo>
<PropertyName>POP_RANGE</PropertyName><Literal>4</Literal></PropertyIsEqualTo></AND></Filter>

• Logical operator NOT

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&
TYPENAME=popplace&Filter=<Filter><AND><NOT><PropertyIsEqualTo><PropertyName>POP_RANGE</PropertyName>
<Literal>2</Literal></PropertyIsEqualTo></NOT><NOT><PropertyIsEqualTo><PropertyName>POP_RANGE</PropertyName>
<Literal>3</Literal></PropertyIsEqualTo></NOT></AND></Filter> 

• Spatial operator BBOX

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&TYPENAME=popplace&
Filter=<Filter><BBOX><PropertyName>Name>NAME</PropertyName><Box%20srsName='EPSG:42304'>
<coordinates>2518000,150000 2918000,450000</coordinates></Box></BBOX></Filter>

• Spatial operator Dwithin

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&TYPENAME=popplace&Filter=
<Filter><DWithin><PropertyName>Geometry</PropertyName><gml:Point><gml:coordinates>2587598.000000,404010.531250</gml:coordinates>
</gml:Point><Distance units='m'>1000</Distance></DWithin></Filter>

• Spatial operator Intersects

http://www2.dmsolutions.ca/cgi-bin/mswfs_filter?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&TYPENAME=popplace&Filter=<Filter>
<Intersect><PropertyName>Geometry</PropertyName><gml:Polygon><gml:outerBoundaryIs><gml:LinearRing>
<gml:coordinates>2488789,289552 2588789,289552 2588789,389552 2488789,389552 2488789,289552</gml:coordinates>
</gml:LinearRing></gml:outerBoundaryIs></gml:Polygon></Intersect></Filter>

• Tests using MapServer as a WFS client and a WFS server are available at http://www2.dmsolutions.ca/msapps/wfs_fe/.
• The OGC conformance tests (http://cite.occamlab.com/tsOGC/) have been run on the FE support. The following table and notes reflect the current status.

Table 2. WFS OGC test suite (over the HTTP Get and Post method)

The OGC Cite WFS test suite can be found on the OGC Cite portal.

Following are some MapServer specific notes on this test suite:

1. Test number 1.3.1:
   • There is a contradiction between the wfs/1.0.0/basic/getfeature/post/3 assertion and the XPath expected value of the test. The assertion says: "Test that a GetFeature request with no output format defined returns a wfs:FeatureCollection with GML data." and the expected XPath value for this request: "boolean(/ogc:ServiceExceptionReport)" is supposed to be true. So, the assertion means that when a WFS server receives a request which contains an undefined output format or no output format at all, the WFS server must return a WFS collection containing GML data. The XPath expected value means that when a WFS server receives a request with an undefined output format or no output format at all, the WFS server must return a service exception report.
2. Tests number 1.3.2 and 1.3.3:
   • Not supported.
3. Tests number 1.3.4.2, 1.3.4.4 to 1.3.4.7 (see bug 461 on MapServer Web site):
   • The string comparison is not supported using >, <, >=, <=.
   • The date comparison is not supported.
4. Test number 1.3.4.10:
   • This property is not supported in MapServer.
5. Test number 1.3.6.1 (see bug 461 on MapServer Web site):
   • The returned feature xml won't validate because the validation is done against a specific xsd (geomatry.xsd).
   • The data conversion on multipoints and multilayers are not supported within gdal.
6. Test number 2:
   • The transaction requests are not supported.

7   About This Document