> 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/form-hierarchy.md).

# Form hierarchy

Where more than one Form value applies for a single topographic area polygon, the population of Primary Form and Secondary Form attributes is driven by a hierarchy. This hierarchy is applied to the data to determine which form is primary and secondary in cases where more than one form applies for a single topographic area polygon. Not all polygons will have a form and this hierarchy only applies where more than one form exists.

The hierarchy has been developed to ensure the process applies the appropriate forms consistently and does not imply any level of priority.

The following table declares this hierarchy:

| Hierarchy | Form                 |
| --------- | -------------------- |
| 1         | Open Semi-Natural    |
| 2         | Inland Water         |
| 3         | Woodland             |
| 4         | Beach Or Foreshore\* |
| 5         | Manmade Surface      |
| 6         | Multi-Surface        |

\*Due to the way beach and foreshore polygons are located, areas with this form would not be expected to have a secondary form.


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