# How the product fits together

OS MasterMap Highways Network – Roads is a relational product. This results in there being relationships between different feature types.

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

<table data-full-width="true"><thead><tr><th width="293">Source Feature Information</th><th>Foreign Key Attribute</th><th>Destination Feature Information</th><th>Primary Key Attribute</th></tr></thead><tbody><tr><td><strong>Feature Type</strong></td><td><strong>—</strong></td><td><strong>Feature Type</strong></td><td><strong>—</strong></td></tr><tr><td>RoadLink</td><td>startNode</td><td>RoadNode</td><td>id</td></tr><tr><td>RoadLink</td><td>endNode</td><td>RoadNode</td><td>id</td></tr><tr><td>RoadLink</td><td>relatedRoadArea</td><td>TopographicArea</td><td>TOID</td></tr><tr><td>RoadLink</td><td>formsPartOf</td><td>Road</td><td>id</td></tr><tr><td>RoadLink</td><td>formsPartOf</td><td>Street</td><td>id</td></tr><tr><td>RoadNode</td><td>relatedRoadArea</td><td>TopographicArea</td><td>TOID</td></tr><tr><td>Road</td><td>link</td><td>RoadLink</td><td>id</td></tr><tr><td>Street</td><td>link</td><td>RoadLink</td><td>id</td></tr><tr><td>RoadJunction</td><td>node</td><td>RoadNode</td><td>id</td></tr><tr><td>FerryTerminal</td><td>element</td><td>RoadNode</td><td>id</td></tr><tr><td>FerryTerminal</td><td>element</td><td>FerryNode</td><td>id</td></tr><tr><td>FerryTerminal</td><td>refToFunctionalSite</td><td>FunctionalSite</td><td>id</td></tr><tr><td>FerryLink</td><td>startNode</td><td>FerryNode</td><td>id</td></tr><tr><td>FerryLink</td><td>endNode</td><td>FerryNode</td><td>id</td></tr></tbody></table>

<figure><img src="/files/LQSHgUfzcbqs6f2ySIOV" alt="Diagram of relational model for OS MasterMap Highways Network - Roads."><figcaption><p>OS MasterMap Highways Network – Roads relational model</p></figcaption></figure>


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