The FEWS Web Feature is the Delft-FEWS implementation of the OpenGIS WFS 2.0 OGC standard and is available since 2023.01. It allows requesting GML or GeoJSON feature data for from plots that have been configured in the Delft-FEWS grid displayGrid Display. The WFS service can be seen as a complementary to the WMS service, as it supports only gridplot types that contain polygon data instead of grids, where the vector data (e.g. polygons, polylines, points; currently only implemented for polygon features) instead of gridded data. The WMS service allows you to render these plots (feature or gridded data) to images, the WFS service provides access to the underlying vector data.

Only gridPlot items that have been configured in the grid display Grid Display configuration to show polygon data can be currently be accessed as a WMS WFS 'Feature Type'. Additional geographic information like configured LocationSets and s(hapefile) Map point and polyline map layers may also become available this way in the near future.

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The official OpenGIS documentation consists of two documents, : the OpenGIS Web Feature Service 2.0 Interface Standard and the OpenGIS Filter Encoding 2.0 Encoding Standard, both of which are ISO certified standards.

WFS Request methods

The available request methods with their supported parameters are described here.

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GetCapabilities

Get a list of the available polygon gridPlots, in . In WFS terminology these are 'FeatureTypes" and other information about the service. GetCapabilties GetCapabilities will return its content as XML in accordance with the WFS 2.0 standard. Only the version 2.0 version of this standard is supported.

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When requesting the GetCapabilities, an XML response with be given with all available polygon gridPlots. The XML schema unfortunately does not allow them to be nested by gridPlotGroups (unlike the WMS schema).

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Code Block

<?xml version="1.0" encoding="UTF-8"?>
<WFS_Capabilities version="2.0.0" xmlns="http://www.opengis.net/wfs/2.0" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:fes="http://www.opengis.net/fes/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:deltares="http://deltares.nl" xsi:schemaLocation="http://www.opengis.net/wfs/2.0 http://schemas.opengis.net/wfs/2.0/wfs.xsd http://www.opengis.net/ows/1.1 http://schemas.opengis.net/ows/1.1.0/owsAll.xsd">
    <ows:ServiceIdentification>
        <ows:Title>WFS Unit tests</ows:Title>
        <ows:ServiceType>WFS</ows:ServiceType>
        <ows:ServiceTypeVersion>2.0.0</ows:ServiceTypeVersion>
    </ows:ServiceIdentification>
    <ows:ServiceProvider>
        <ows:ProviderName>Deltares</ows:ProviderName>
    </ows:ServiceProvider>
    <ows:OperationsMetadata>
        <ows:Operation name="GetCapabilities">
            <ows:DCP>
                <ows:HTTP>
                    <ows:Get xlink:href="http://localhost/FewsWebServices/wfs"></ows:Get>
                </ows:HTTP>
            </ows:DCP>
            <ows:Parameter name="AcceptVersions">
                <ows:AllowedValues>
                    <ows:Value>2.0.0</ows:Value>
                </ows:AllowedValues>
            </ows:Parameter>
            <ows:Parameter name="AcceptFormats">
                <ows:AllowedValues>
                    <ows:Value>text/xml</ows:Value>
                </ows:AllowedValues>
            </ows:Parameter>
        </ows:Operation>
        <ows:Operation name="DescribeFeatureType">
            <ows:DCP>
                <ows:HTTP>
                    <ows:Get xlink:href="http://localhost/FewsWebServices/wfs"/>
                </ows:HTTP>
            </ows:DCP>
            <ows:Parameter name="outputFormat">
                <ows:AllowedValues>
                    <ows:Value>application/gml+xml; version=3.2</ows:Value>
                </ows:AllowedValues>
            </ows:Parameter>
        </ows:Operation>
        <ows:Operation name="ListStoredQueries">
            <ows:DCP>
                <ows:HTTP>
                    <ows:Get xlink:href="http://localhost/FewsWebServices/wfs"/>
                </ows:HTTP>
            </ows:DCP>
        </ows:Operation>
        <ows:Operation name="DescribeStoredQueries">
            <ows:DCP>
                <ows:HTTP>
                    <ows:Get xlink:href="http://localhost/FewsWebServices/wfs"/>
                </ows:HTTP>
            </ows:DCP>
        </ows:Operation>
        <ows:Operation name="GetFeature">
            <ows:DCP>
                <ows:HTTP>
                    <ows:Get xlink:href="http://localhost/FewsWebServices/wfs"/>
                </ows:HTTP>
            </ows:DCP>
            <ows:Parameter name="outputFormat">
                <ows:AllowedValues>
                    <ows:Value>application/gml+xml; version=3.2</ows:Value>
                    <ows:Value>application/geo+json</ows:Value>
                    <ows:Value>application/json</ows:Value>
                </ows:AllowedValues>
            </ows:Parameter>
        </ows:Operation>
        <ows:Parameter name="AcceptVersions">
            <ows:AllowedValues>
                <ows:Value>2.0.0</ows:Value>
            </ows:AllowedValues>
        </ows:Parameter>
        <ows:Constraint name="ImplementsBasicWFS">
            <ows:NoValues/>
            <ows:DefaultValue>TRUE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsTransactionalWFS">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsLockingWFS">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="KVPEncoding">
            <ows:NoValues/>
            <ows:DefaultValue>TRUE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="XMLEncoding">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="SOAPEncoding">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsInheritance">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsRemoteResolve">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsResultPaging">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsStandardJoins">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsSpatialJoins">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsTemporalJoins">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ImplementsFeatureVersioning">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="ManageStoredQueries">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
        <ows:Constraint name="wfs:StoredQuery">
            <ows:NoValues/>
            <ows:DefaultValue>FALSE</ows:DefaultValue>
        </ows:Constraint>
    </ows:OperationsMetadata>
    <FeatureTypeList>
        <FeatureType>
            <Name>deltares:full_extent_cta_clean</Name>
            <Title>SFINCS full extent</Title>
            <DefaultCRS>urn:ogc:def:crs:EPSG::4326</DefaultCRS>
            <OtherCRS>urn:ogc:def:crs:EPSG::4326</OtherCRS>
            <OtherCRS>urn:ogc:def:crs:EPSG::3857</OtherCRS>
            <ows:WGS84BoundingBox>
                <ows:LowerCorner>125.095000 -37.527500</ows:LowerCorner>
                <ows:UpperCorner>153.637500 -10.020000</ows:UpperCorner>
            </ows:WGS84BoundingBox>
        </FeatureType>
        <FeatureType>
            <Name>deltares:full_extent_cta</Name>
            <Title>SFINCS full extent (not clean)</Title>
            <DefaultCRS>urn:ogc:def:crs:EPSG::4326</DefaultCRS>
            <OtherCRS>urn:ogc:def:crs:EPSG::4326</OtherCRS>
            <OtherCRS>urn:ogc:def:crs:EPSG::3857</OtherCRS>
            <ows:WGS84BoundingBox>
                <ows:LowerCorner>125.095000 -37.527500</ows:LowerCorner>
                <ows:UpperCorner>153.637500 -10.020000</ows:UpperCorner>
            </ows:WGS84BoundingBox>
        </FeatureType>
    </FeatureTypeList>
</WFS_Capabilities>

Note: in this example a A Deltares namespace is used in this example to identify items that originate from Delft-FEWS, as identified by xmlns:deltares="http://deltares.nl". This is used as prefix for the gridplot-id values that have been taken from the spatial display configuration, . The WFS standard more or less requires this. The namespace used by the WFS service can be changed in the WebservicesWebServices.xml configuration.

GetFeature

Get the polygon GridPlot vector data in GML or GeoJSON format, the . The GridPlot to get is specified by the FeatureTypes parameter.

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typeNames (required): the gridPlot id of the plot to display. Only one gridPlot id is supported.
version (optional): supported version is 2.0 and is the default if not set. Older versions are not supported.
crs (optional, 'EPSG:4326' is the default): the output projection of the plot. The default projection used by FEWS is always EPSG:4326 (unprojected WGS84 geographic coordinates; longitude, latitude). Other projections coordinate systems are supported only if they are configured in webservicesWebServices.,xml.
bbox (optional): the bounding box (in the projection as defined by the CRS parameter) of the extent of interest. Any features that intersect the BBOX will be returned. Features that lie completely lie outside the BBOX area will not be returned.
filter (optional): a filter expression in encoded xml XML format as specified in the OpenGIS Filter Encoding 2.0 Encoding Standard, only . Only the "Minimum Standard Filter" conformance class is currently implemented and has been tested.
for For more information see the section about filtering , refer to WFS Request Filtering below.
format (optional, 'application/gml+xml; version=3.2' is the default): GML is the standard output format that any WFS implementation must support, optionally . Optionally 'application/geo jsongeojson' can be requested , which instead. Geojson is more compact and generally easier to process..

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Vendor-specific request parameters

time (optional): the time for which associated with the polygon data is being requested. Only one time is supported. Time ranges are NOT supported. Time has to be in the xml dateformatXML date format: yyyy-MM-ddTHH:mm:ssZ. The time parameter is identical to that of the Delft-FEWS WMS service for practical reasons. If no time parameter is specified, the most recent (current) forecast data will be returned.
Please note that any options the OpenGIS Filter specifications offer to define a temporal extent have not yet been implemented in the Delft-FEWS WFS at this moment.
cql_filter (optional): similar to the filter parameter, a filter expression in CQL (Common Query Language) syntax can be specified to request only a subset of features. This syntax is easier to use than the XML filter syntax, for more information see the section about filtering . For more information, refer to WFS Request Filtering below.

Restrictions:

There currently are no restrictions on the output size of the WFS service, paging . Paging options that may help dealing with very large datasets have not yet been implemented.

Response

GML 3 GML3 or GeoJSON vector data of the requested polygon gridPlot for the specified time. if If no time is specified, the last available timestep time step will be returned.

Example request

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The typical response in GML or GeoJSON for polygon date data is too large to be displayed here.

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Provides a detailed description of one or more feature types, the . The most important function of this request is to list the available feature attributes (Delft-FEWS timeseries timeSeries properties). The output format is a an XML schema.

Request parameters

typeNames (required): the gridPlot id of one or more plots to display. if If this is not specified, a list of feature types is provided as a list of uri's.
version (optional): supported version is 2.0 and is the default if not set. Older versions are not supported.

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Get a list of 'stored queries' a WFS supports, in this case the . The only stored query supported is the so-called "GetFeatureById" stored query. This request has been implemented as the WFS 2.0 lists it as because it is a requirement for the "Simplesimple" implementation of a WFS 2.0 service. Note: The id's

The ids, used mainly for the generation of GML output, are assigned sequentially, ; they are not linked to a specific property or attribute in Delft-FEWS.

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Get a more detailed description of the 'stored queries' a that the WFS supports, in this case the . The only stored query supported is the so-called "GetFeatureById" stored query. This request has been implemented as the WFS 2.0 lists it as because it is a requirement for the "Simplesimple" implementation of a WFS 2.0 service. Note: The id's

The ids, used mainly for the generation of GML output, are assigned sequentially, ; they are not linked to a specific property or attribute in Delft-FEWS.

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version (optional): supported version is 2.0 and is the default if not set. Older versions are not supported.

Example request

Code Block
http://localhost:8080/FewsWebServices/wfs?service=wfs&request=DescribeStoredQueries

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An important feature of the GetFeature request is filtering, which allows a subset of a feature set to be requested based on the feature properties/attributes, spatial extent, and/or time. The filtering parameters that can be applied are;:

time
bbox
filter
cql_filter

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TIME

The filtering using the TIME parameter works the same was as it does for the Delft-FEWS WMS service, a . A time parameter can be given on the request url in the format yyyy-MM-ddTHH:mm:ssZ ssZ

Polygon-based plots in the Delft-FEWS spatial display Spatial Display configuration are typically are timeseries timeSeries of polygons, so by . By using the TIME parameter you can request the polygons that are in the datastore for a specific timestep. If no TIME parameter is specified, the polygon for the most recent timestep will be returned. It currently is not currently possible to request a timeseries multiple time steps (a timeSeries) of polygons in a single request. Instead, a separate request for each timestep in a timeseries would be timeSeries is required.

Example request using the TIME parameter

Code Block
<to be added>

BBOX

The BBOX (Bounding box) filter also works the same way as it does for the WMS service, by specifying BOX) filter allows you to specify a rectangular area in the form format BBOX=<minX>,<minY>,<maxX>,<maxY> you can request . This will return only the features that partially or completely overlap intersect that rectangular area. If a CRS parameter is provided to the GetFeature request to request return the data in a specific cartographic projection, the bounding box coordinates should also be provided in that projection.

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Example request using the BBOX parameter

Code Block
<to be added>

FILTER

The standard FILTER parameter, which is part of the official OpenGIS WFS 2.0 specification, uses a an XML-based syntax, which has been is documented in a separate document, OpenGIS Filter Encoding 2.0 Encoding Standard.

Only the "Minimum Standard Filter" conformance class is currently implemented, which means that the logical operators PropertyIsEqualTo, PropertyIsNotEqualTo, PropertyIsLessThan, PropertyIsGreaterThan,
PropertyIsLessThanOrEqualTo, and PropertyIsGreaterThanOrEqualTo can be used and chained together using And / Or operators.

Now the The problem with the standard XML-based filter syntax is that the Delft-FEWS WFS implementation at this point currently only supports http GET methods, where in which all request parameters need to be passed on on via the request url using NVP (Name-Value pairPair) syntax, and the XML for the filter parameter needs to be 'URL encoded".

Example request using the FILTER parameter

For To give an example, a project where the polygons have a property 'region_id' one could specify a filter for the WFS getFeature request in XML like like this:

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This syntax is more or less unusable for manually putting together or interpreting WFS requests using filters. Fortunately, fortunately the CQL_FILTER parameter syntax (below) is more practical.

Code Block
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CQL_

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FILTER

The CQL_Filter parameter uses the Common Query Language format, which was developed by the OGC consortium as part of the Catalogue Service for the Web specification (CSW) and is, for example, implemented by Geoserver, which is commonly considered the reference implementation of the WFS protocol. So the The CQL_Filter FILTER parameter for the GetFeature request is therefore not part of the official standard specifications, but strongly recommended for use in http GET requests. A nice overview of the CQL syntax is provided in the Geoserver documentation, however a warning is in place that not all possible filters mentioned there are currently supported and only the simple logical operators like in the above example have been tested.

Example request using the CQL_FILTER parameter

The filter that was used as an example in the previous section in CQL syntax looks like this:

CQL_FILTER=region_id='123'

Multiple logical operators can be grouped together using AND / OR like this:

CQL_FILTER=region_id='123'+OR+region_id='124'A nice overview of the CQL syntax is provided in the Geoserver documentation, however a warning is in place that not all possible filters mentioned there are currently supported and only the simple logical operators like in the above example have been tested at this point.

Code Block
<to be added>

Properties

The following WFS specific properties can be configured in the webservices.xml configuration:

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Properties

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Vendor-specific request parameters

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