> 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/products/land-and-terrain-portfolio/os-mastermap-greenspace-layer/os-mastermap-greenspace-layer-technical-specification/gml-overview.md).

# GML overview

The OS MasterMap Greenspace Layer product is supplied in Geography Markup Language (GML) version 3.2.1. This section describes how OS MasterMap Greenspace Layer is defined in GML. An understanding of XML (eXtensible Mark-up Language) and XML schemas is required.

## GML <a href="#id-4.1-gml" id="id-4.1-gml"></a>

GML is an XML grammar for expressing geographic features. GML serves as a modelling language for geographic systems as well as an open interchange format for geographic transactions on the Internet. More information can be found on the Open Geospatial Consortium (OGC). <http://www.opengeospatial.org/standards/gml>.

The XML specifications that GML is based on are available from the World Wide Web Consortium (W3C): [http://www.w3.org](http://www.w3.org/).

Information about Unicode and UTF-8, the character encoding we have chosen, is available on the Unicode Consortium website: [http://www.unicode.org](http://www.unicode.org/).

### Use of examples <a href="#id-4.2-use-of-examples" id="id-4.2-use-of-examples"></a>

Any use of examples in this chapter that mention specific data content are to be taken as examples only.

### Schema overview and location <a href="#id-4.3-schema-overview-and-location" id="id-4.3-schema-overview-and-location"></a>

XML schemas are used to define and validate the format and content of the 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 schema document defines the namespace, `http://namespaces.ordnancesurvey.co.uk/OSMM/Greenspace/1.0`, this is defined in the XSD at: [https://www.ordnancesurvey.co.uk/xml/open/ogsp/1.0/OSMMGreenspace.xsd.](https://www.ordnancesurvey.co.uk/xml/open/ogsp/1.0/OSMMGreenspace.xsd)

### Code list dictionaries <a href="#id-4.4-code-list-dictionaries" id="id-4.4-code-list-dictionaries"></a>

The code list dictionaries for the OS MasterMap Greenspace Layer can be found at the following URLs: <http://www.os.uk/xml/codelists/GreenspaceFunctionValue.xml> <http://www.os.uk/xml/codelists/FormValue.xml>


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