SLD

<?xml version="1.0" encoding="UTF-8"?>
<sld:StyledLayerDescriptor version="1.0.0"
  xsi:schemaLocation="http://www.opengis.net/sld StyledLayerDescriptor.xsd"
  xmlns="http://www.opengis.net/sld"
  xmlns:ogc="http://www.opengis.net/ogc"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:sld="http://www.opengis.net/sld">
    <sld:UserLayer>
        <sld:LayerFeatureConstraints>
            <sld:FeatureTypeConstraint/>
        </sld:LayerFeatureConstraints>
        <sld:UserStyle>
            <sld:Name>OWM Icons</sld:Name>
            <sld:FeatureTypeStyle>
                <sld:Rule>
                    <sld:Name>OWM Icons</sld:Name>
                    <sld:Title>OWM Icons</sld:Title>
                    <ogc:Filter>
                        <ogc:PropertyIsEqualTo>
                            <ogc:PropertyName>active_internal</ogc:PropertyName>
                            <ogc:Literal>true</ogc:Literal>
                        </ogc:PropertyIsEqualTo>
                    </ogc:Filter>
                    <PointSymbolizer>
                        <Graphic>
                            <Mark>
                                <WellKnownName>circle</WellKnownName>
                                <Fill>
                                    <CssParameter name="fill">#000000</CssParameter>
                                </Fill>
                            </Mark>
                            <Opacity>
                                0.1
                            </Opacity>
                            <Size>1</Size>
                        </Graphic>
                    </PointSymbolizer>
                    <TextSymbolizer>
                        <Label>
                            <![CDATA[ ]]>
                        </Label>
                        <LabelPlacement>
                            <PointPlacement>
                                <AnchorPoint>
                                    <AnchorPointX>0.5</AnchorPointX>
                                    <AnchorPointY>0.5</AnchorPointY>
                                </AnchorPoint>
                                <Displacement>
                                    <DisplacementX>0</DisplacementX>
                                    <DisplacementY>0</DisplacementY>
                                </Displacement>
                            </PointPlacement>
                        </LabelPlacement>
                        <Fill>
                            <CssParameter name="fill">#000000</CssParameter>
                        </Fill>
                        <sld:Graphic>
                            <sld:ExternalGraphic>
                                <sld:OnlineResource xlink:type="simple"
                                    xlink:href="http://openweathermap.org/img/w/${icon}.png"/>
                                <sld:Format>image/png</sld:Format>
                            </sld:ExternalGraphic>
                            <sld:Size>50</sld:Size>
                        </sld:Graphic>
                    </TextSymbolizer>
                </sld:Rule>
            </sld:FeatureTypeStyle>
        </sld:UserStyle>
    </sld:UserLayer>
</sld:StyledLayerDescriptor>