> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/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-downloads/resources/product-resources/end-of-life-product-documentation/os-detailed-path-network/os-detailed-path-network-technical-specification/gml-overview.md).

# GML overview

## Schema overview and location <a href="#bookmark58" id="bookmark58"></a>

XML schemas are used to define and validate the format and content of the Geography Markup Language (GML). The GML v3.2.1 specification provides a set of schemas that define the GML feature constructs and geometric types. These are designed to be used as a basis for building application-specific schemas, which define the data content.

The ‘OS Detailed Path Network’ schema document defines the `http://namespaces.os.uk/networks/detailedPathNetwork/1.0` Namespace.

These schemas make use of XSDs (XML schema definitions) produced by the W3C; these [XSDs are](http://www.w3.org/XML/1998/namespace.html) [available from the W3C website](http://www.w3.org/XML/1998/namespace.html).

The application schema uses the following XML namespaces, for which definitions are available in the table below:

#### *The XML namespaces used by the application schema and their definitions.*

<table><thead><tr><th>Prefix</th><th width="268">Namespace identifier</th><th>Definition available at</th></tr></thead><tbody><tr><td>gml</td><td><code>http://www.opengis.net/gml</code></td><td><a href="http://schemas.opengis.net/gml/3.2.1/gml.xsd">http://schemas.opengis.net/gml/3.2.1/gml.xsd</a></td></tr><tr><td>Xsi</td><td><code>http://www.w3.org/2001/XMLSchema–instance</code></td><td>Built into XML, see <a href="http://www.w3.org/TR/xmlschema-1/">http://www.w3.org/TR/xmlschema-1/</a></td></tr><tr><td>xlink</td><td><code>http://www.w3.org/1999/xlink</code></td><td><a href="http://www.w3.org/1999/xlink.xsd">http://www.w3.org/1999/xlink.xsd</a></td></tr></tbody></table>

### Simple Features Profile – Level 1 <a href="#bookmark59" id="bookmark59"></a>

GML is designed to support a wide variety of capabilities, ranging from simple contextual mapping, such as OS Open Map, to products that include complex geometric property types or even spatial and temporal topology.

[The Simple Features Profile of GML 3.2.1](https://portal.ogc.org/modules/admin/license_agreement.php?suppressHeaders=0\&access_license_id=3\&target=http%3A//portal.opengeospatial.org/files/%3fartifact_id%3D15201) defines a restricted subset of GML, allowing scope for greater interoperability.

This product conforms to Simple Features Profile – Level 1.


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