FES - Filter Encoding SpecificationFiltering WFS Layers in CCSS Geoportal

Filter Encoding Standard enables you to create XML filter expressions and is incorporated in the WFS standard.

In CCSS Geoportal the FES is used with the help of OWSProxy to filter the WFS layers.

How to use it

- Add a WFS Layer

- In the layer switcher, right-click on the layer name and select “Filter”

How to use it

How to use it

- Filter window appears with comparison filter

- Select the property name, comparison operator and type in the desired value

- Apply the filter

How to use it

How does it work

How does it work

WFS layers are displayed as WMS in the HSLayers Web Client (see OWSProxy for details).

1. WFS GetCapabilities request is sent directly to the WFS server. Capabilities document is parsed, especially the <Filter_Capabilities> section.

2. WFS DescribeFeatureTypes is sent to get the properties of the WFS features.

3. User creates the filter in the GUI

How does it work

4. New WMS request is sent to OWSProxy, accompanied with FES filter in an additional parameter.

5. OWSProxy takes the filter, creates WFS request and sends it to the WFS server. Server replies with filtered layer.

6. OWSProxy transforms the returned WFS layer to WMS and sends it to the client.

Next Steps

So far, only FES 1.1.0 has been implemented in terms of standards and only the comparison filter is supported in the GUI.

As next steps, the implementation of FES 1.0.0 is foreseen as well as additional support for time.

In the GUI, more filters can be added. That means the logical filter enabling to combine various expressions, spatial filter, expression editor, filtering based on feature ids, support for server-side functions.