# Restricting to a main category

As the Navigation module works with exactly the same data as the search, the navigation of the product range corresponds to a given filter or combination of filters over the entire product range. The types of fields filtered here are key. There are two types of fields in FactFinder:

#### Simple data field

Each simple data field contains the information stored in a single level. A FactFinder environment that uses this type of category structure has several associated fields that make up the hierarchy. Normally, these carry the same name and are differentiated by a numbering scheme (such as `Category0, Category1, Category2`).

Example data:

|            |                  |
| ---------- | ---------------- |
| Field name | Database content |
| category0  | Clothing         |
| category1  | Trousers         |
| category2  | Jeans            |

#### Category path field

In this case, the complete navigation hierarchy is stored in a specially defined FactFinder category path field. Please be aware that the database content does not correspond to the content of the export file (details concerning the export format can be found in the Export documentation).

|            |                             |
| ---------- | --------------------------- |
| Field name | Database content            |
| category   | \|Clothing/Trousers/Jeans\| |

### Filtering for a simple data field

The default name of this sort of field in FactFinder is `category0`. If you want to navigate (filter) to the category with the name `Clothing`, the navigation call must pass a filter parameter with the name `filter=category0:{value}` and the value `Clothing`. A corresponding call to the REST interface would be:

```language-plaintext
..rest/{apiversion}/navigation/{channel}?filter=category0:Closing
```

### Filtering for a category path field

If you want to navigate a data field that contains a category path, the navigation call must pass a filter parameter with the name `filter=category:{value}` and the value `Clothing`.

In relation to the example above, a corresponding call to the REST interface would be:

```language-plaintext
$stringEscapeUtils.escapeHtml($body)
```


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