GML overview

This section describes how OS MasterMap is defined in GML. An understanding of XML (Extensible Markup Language) and XML schema is required.

GML

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.

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

Schema overview and location

XML schemas are used to define and validate the format and content of GML. The GML 3.2 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 MasterMap Highways Network RAMI product uses the following application schemas, which are referenced by the data:

• RoutingAndAssetManagement.xsd

• GeneralNetwork.xsd

• OSProducts.xsd

The RoutingAndAssetManagement.xsd defines the features which make up the RAMI features. Therefore, it imports the INSPIRE transport network road application schema.

The GeneralNetwork.xsd defines how the RAMI features reference back to the network. Therefore, it imports the INSPIRE network application schema. Through the INSPIRE schemas, both the RoutingAndAssetManagement.xsd and GeneralNetwork.xsd import the GML 3.2 schemas. These in turn import schemas produced by the W3C, which are available from the W3C website at http://www.w3.org/XML/1998/namespace.html.

The OSProducts.xsd defines the feature collection and feature members. In addition, this application schema will define the transactions used for a COU supply.

The RAMI schema document defines the http://namespaces.os.uk/mastermap/routingAndAssetManagement/2.1 namespace;

this is defined in the XSD at: http://www.os.uk/xml/schema/highwaysnetwork/2.1/RoutingAndAssetManagement.xsd.

The General Network schema document defines the http://namespaces.os.uk/mastermap/generalNetwork/2.0 namespace;

this is defined in the XSD at: https://www.ordnancesurvey.co.uk/xml/schema/network/2.0/generalNetwork.xsd.

The Highways Dedication schema document defines the http://namespaces.os.uk/mastermap/highwayDedication/1.0 namespace;

this is defined in the XSD at: https://www.ordnancesurvey.co.uk/xml/schema/highwaysnetwork/1.0/HighwayDedication.xsd.

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

Prefix	Namespace identifier	Definition available at
gml	http://www.opengis.net/gml	http://schemas.opengis.net/gml/3.2.1/gml.xsd
xsi	http://www.w3.org/2001/XMLSchema– instance	Built in to XML http://www.w3.org/TR/xmlschema-1/
xlink	http://www.w3.org/1999/xlink	http://www.w3.org/1999/xlink.xsd
net	http://inspire.ec.europa.eu/schemas/net/4.0	http://inspire.ec.europa.eu/schemas/net/4.0/Netw ork.xsd
tn	http://inspire.ec.europa.eu/schemas/tn/4.0	http://inspire.ec.europa.eu/schemas/tn/4.0/Comm onTransportElements.xsd
tn-ro	http://inspire.ec.europa.eu/schemas/tn- ro/4.0	http://inspire.ec.europa.eu/schemas/tn- ro/4.0/RoadTransportNetwork.xsd
tn-w	http://inspire.ec.europa.eu/schemas/tn- w/4.0	http://inspire.ec.europa.eu/schemas/tn- w/4.0/WaterTransportNetwork.xsd
os	http://namespaces.os.uk/product/1.0	http://www.ordnancesurvey.co.uk/xml/schema/pr oduct/1.0/OSProduct.xsd
network	http://namespaces.os.uk/mastermap/highw ayNetwork/2.0	http://www.os.uk/xml/schema/highwaysnetwork/ 2.0/LinearHighwayNetwork.xsd
ram	http://namespaces.os.uk/mastermap/routin gAndAssetManagement/2.1	http://www.os.uk/xml/schema/highwaysnetwork/ 2.1/RoutingAndAssetManagement.xsd
hwtn	http://namespaces.os.uk/mastermap/highw aysWaterTransportNetwork/1.0	http://www.os.uk/xml/schema/highwaysnetwork/ v1/HighwaysWaterTransportNetwork.xsd
dedication	http://namespaces.os.uk/mastermap/highw ayDedication/1.0	https://www.ordnancesurvey.co.uk/xml/schema/h ighwaysnetwork/1.0/HighwayDedication.xsd