> 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/transport-network-portfolio/os-mastermap-highways-network-routing-and-asset-management-information/os-mastermap-highways-network-routing-and-asset-management-information-technical-specification/how-the-product-fits-together.md).

# How the product fits together

OS MasterMap Highways Network – RAMI is a relational product. This results in there being relationships between different feature types. This section summarises how the different feature types relate to one another, and which attributes are the primary and foreign keys for the RAMI feature. For information on the Roads features, please see the [*Roads Technical Specification*](/os-downloads/products/transport-network-portfolio/os-mastermap-highways-network-roads/os-mastermap-highways-network-roads-technical-specification.md).

The following table identifies how the feature types relate to one another and which attributes are the primary and foreign keys. This is also represented diagrammatically in the figure below the table. The attribute at the arrowhead is the primary key, and the attribute at the base of the arrow is the foreign key.

{% hint style="info" %}

## Foreign key attribute reference

In GML, relationships shown using the element tag are implemented using an `xlink:href` attribute on the relevant element. The `xlink:href` value provides the reference to the related feature.
{% endhint %}

<table data-full-width="true"><thead><tr><th width="253">Source Feature Type</th><th>Foreign Key Attribute</th><th width="229">Destination Feature Type</th><th>Primary Key Attribute</th></tr></thead><tbody><tr><td><strong>Feature Type</strong></td><td>—</td><td><strong>Feature Type</strong></td><td>—</td></tr><tr><td>AccessRestriction</td><td>element</td><td>RoadLink</td><td>id</td></tr><tr><td>TurnRestriction</td><td>element</td><td>RoadLink</td><td>id</td></tr><tr><td>RestrictionForVehicles</td><td>element</td><td>RoadLink</td><td>id</td></tr><tr><td>RestrictionForVehicles</td><td>element</td><td>RoadNode</td><td>id</td></tr><tr><td>RestrictionForVehicles</td><td>linkReference</td><td>RoadLink</td><td>id</td></tr><tr><td>Hazard</td><td>element</td><td>RoadLink</td><td>id</td></tr><tr><td>Hazard</td><td>element</td><td>RoadNode</td><td>id</td></tr><tr><td>Hazard</td><td>linkReference</td><td>RoadLink</td><td>id</td></tr><tr><td>Structure</td><td>element</td><td>RoadLink</td><td>id</td></tr><tr><td>Structure</td><td>element</td><td>RoadNode</td><td>id</td></tr><tr><td>Structure</td><td>linkReference</td><td>RoadLink</td><td>id</td></tr><tr><td>Maintenance</td><td>element</td><td>Street</td><td>id</td></tr><tr><td>Reinstatement</td><td>element</td><td>Street</td><td>id</td></tr><tr><td>SpecialDesignation</td><td>element</td><td>Street</td><td>id</td></tr><tr><td>HighwayDedication</td><td>element</td><td>Street</td><td>id</td></tr><tr><td>HighwayDedication</td><td>element</td><td>RoadLink</td><td>id</td></tr></tbody></table>

<figure><img src="https://1897589978-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcNpJpLP8RROUaWVQo5ea%2Fuploads%2F7kJicZRs5O8cMUvqEM5A%2Fimage.png?alt=media&amp;token=45370d07-d7bd-4448-baff-79ad70bd0a67" alt="Diagram of OS MasterMap Highways Network - Routing and Asset Management Information relational model"><figcaption><p>OS MasterMap Highways Network – Routing and Asset Management Information relational model</p></figcaption></figure>


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