[GIS] Show custom string as label in SLD Geoserver

Question

How is possible to add a custom string to the label of shape in SLD? without any predefined ogc:PropertyName
means I want to add a constant string (in my case " BS") to the field "Area", example: "1200 BC"

there is no PropertyName called "BC"

<Rule>
    <Name>rule 1</Name>
    <Title>Post Label</Title>
    <TextSymbolizer>
      <Label>
        <ogc:Function name="round">
          <ogc:PropertyName>year</ogc:PropertyName>
        </ogc:Function>
      </Label>
      <Font>
        <CssParameter name="font-family">Arial</CssParameter>
        <CssParameter name="font-size">11</CssParameter>
        <CssParameter name="font-style">normal</CssParameter>
        <CssParameter name="font-weight">bold</CssParameter>
      </Font>
      <LabelPlacement>
        <LinePlacement/>
      </LabelPlacement>
      <Fill>
        <CssParameter name="fill">#000000</CssParameter>
      </Fill>
    </TextSymbolizer>
</Rule>

Answer 1

You just ad BC to the label line.

    <TextSymbolizer>
        <Label>
          <ogc:PropertyName>STATE_ABBR</ogc:PropertyName> Ian
        </Label>
        <Font>
          <CssParameter name="font-family">Times New Roman</CssParameter>
          <CssParameter name="font-style">Normal</CssParameter>
          <CssParameter name="font-size">14</CssParameter>
        </Font>
        <LabelPlacement>
          <PointPlacement>
            <AnchorPoint>
              <AnchorPointX>0.5</AnchorPointX>
              <AnchorPointY>0.5</AnchorPointY>
            </AnchorPoint>
          </PointPlacement>
        </LabelPlacement>
      </TextSymbolizer>

Produces a map like: