Module chain in XML

gistfile1.xml

<chain source="ground_select">
  <module type="constant"           name="tile_air"                 value="1.00" />
  <module type="constant"           name="tile_dirt"                value="2.00" />
  <module type="constant"           name="tile_stone"               value="3.00" />
  <module type="constant"           name="tile_copper"              value="4.00" />
  <module type="constant"           name="tile_silver"              value="5.00" />
  <module type="constant"           name="tile_gold"                value="6.00" />
  <module type="constant"           name="tile_bedrock"             value="255.00" />

  <module type="gradient"           name="contour_gradient"         x0="0.00" x1="0.00" y0="0.00" y1="1.00" />
  <module type="fractal"            name="contour_fractal"          fractal_type="fbm" basis_type="gradient" interpolation_type="quintic" octaves="3" frequency="2.00" />
  <module type="cache"              name="contour_fractal_cache"    source="contour_fractal" />
  <module type="scale_offset"       name="contour_scale"            source="contour_fractal_cache" scale="0.50" offset="0.00" />
  <module type="scale_domain"       name="contour_scale_y"          source="contour_scale" ys="0.00" />
  <module type="translate_domain"   name="contour_perturb"          source="contour_gradient" ya="contour_scale_y" />
  
  <module type="scale_offset"       name="contour_overhang_scale"   source="contour_fractal_cache" scale="0.50" offset="0.00" />
  <module type="translate_domain"   name="contour_overhang_perturb" source="contour_perturb" xa="contour_overhang_scale" />
  
  <module type="gradient"           name="ground_gradient"          x0="0.00" x1="0.00" y0="0.00" y1="0.90" />
  <module type="clamp"              name="ground_gradient_clamp"    source="ground_gradient" low="0.00" high="1.00" />
  <module type="fractal"            name="ground_fractal"           fractal_type="ridged_multi" basis_type="gradient" interpolation_type="quintic" octaves="3" frequency="10.00" />
  
  <module type="combiner"           name="ground_gradient_combiner" combiner_type="multiply">
    <source>ground_fractal</source>
    <source>ground_gradient_clamp</source>
  </module>
  
  <module type="select"             name="ground_1"                 source="ground_gradient_combiner" low="tile_dirt" high="tile_stone" threshold="0.50" />
  <module type="select"             name="ground_2"                 source="ground_gradient_combiner" low="ground_1" high="tile_stone" threshold="0.80" />
  <module type="select"             name="ground_select"            source="contour_overhang_perturb" low="tile_air" high="ground_2" threshold="0.50" />
</chain>