> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-apis/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-apis/accessing-os-apis/os-features-api/technical-specification/filtering.md).

# Filtering

The OS Features API service accepts standard OGC XML filter parameters and can be applied following the normal OGC filter structure. When constructing an attribute-based filter, any attribute returned in the `DescribeFeatureType` response is a valid candidate.

For example, to return all `Topography_TopographicArea` features with a `DescriptiveGroup` of `Roadside`, a user would submit a `GetFeature` request with a `typeNames` parameter of `Topography_TopographicArea`, and a `filter` parameter like this:

{% code overflow="wrap" %}

```javascript
<ogc:Filter>
  <ogc:PropertyIsEqualTo>
    <ogc:PropertyName>DescriptiveGroup</ogc:PropertyName>
    <ogc:Literal>Roadside</ogc:Literal>
  </ogc:PropertyIsEqualTo>
</ogc:Filter>
```

{% endcode %}

{% hint style="info" %}
**Note**:

If you want to combine both a bounding box and another filter each should be included in a single OGC filter parameter. If you combine a purely attribute-based OGC filter (as above) with a bounding box via the `bbox` request parameter, the `bbox` request parameter takes precedence and the attribute filter is ignored.
{% endhint %}

A combined bounding box and attribute filter might look something like this:

{% code overflow="wrap" %}

```javascript
<ogc:Filter>
  <ogc:And>
    <ogc:Within>
      <PropertyName>SHAPE</PropertyName>
      <gml:Box xmlns:gml="http://www.opengis.net/gml" srsName="EPSG:27700">
        <gml:coordinates decimal="." cs="," ts=",">
          436833.50,115334.90,437643.25,115761.50
        </gml:coordinates>
      </gml:Box>
    </ogc:Within>
    <ogc:PropertyIsEqualTo>
      <ogc:PropertyName>DescriptiveGroup</ogc:PropertyName>
      <ogc:Literal>Roadside</ogc:Literal>
    </ogc:PropertyIsEqualTo>
  </ogc:And>
</ogc:Filter>
```

{% endcode %}


---

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