# Category taxonomy uses controlled vocabulary, not freeform text

- **Pattern:** `ab-001025` (`directory-listing-schema.content-completeness.category-taxonomy`)
- **Severity:** high
- **Lifecycle:** active
- **Last modified:** 2026-04-18
- **Canonical URL:** https://auditbuffet.com/patterns/ab-001025
- **License:** CC-BY-4.0 — attribute to AuditBuffet Pattern Catalog (https://auditbuffet.com/patterns/ab-001025)

## Why it matters

Free-text categories produce `Restaurant`, `restaurant`, `Restaraunt`, and `Food` as four distinct buckets for the same concept. Your browse pages fragment, faceted filters break, sitemaps balloon with near-duplicate URLs that Google treats as keyword cannibalization, and analytics reports become impossible to trust. Once inconsistent data lands in the database, deduplication is a manual SQL cleanup job that costs far more than enforcing a controlled vocabulary at submission time. Schema.org `Category` emitters also require stable enum values.

## Severity rationale

High because free-text taxonomies fragment browse pages, break filters, and create SEO cannibalization that worsens with scale.

## Remediation

Replace the free-text input with a select backed by a canonical enum or category table, and validate the submitted value against that list on the server. Store categories as a foreign-key reference or a constrained string column so the database rejects rows with values outside the vocabulary. Define the enum in `src/lib/taxonomy/categories.ts` and import it in both the form and the API handler.

```ts
export const CATEGORIES = ['restaurant', 'cafe', 'retail', 'services'] as const
export const CategorySchema = z.enum(CATEGORIES)
```

Seed a category table with the same values and add a CHECK constraint or FK.

## Detection

- **ID:** `category-taxonomy`
- **Severity:** `high`
- **What to look for:** List all category values used across listings. For each category, check the category field in the submission form or schema. Is it a dropdown/select from a predefined list, or a free-form text input? Sample the data and look for category values that might be typos or duplicates.
- **Pass criteria:** Categories are selected from a controlled vocabulary (dropdown, select, or predefined enum) and are not free-form text input — 100% of categories must come from a defined taxonomy or enumeration, not free text. Report: "X unique categories found, all Y from a defined taxonomy."
- **Fail criteria:** Categories are stored as free-form text, allowing inconsistent, misspelled, or duplicate categories.
- **Skip (N/A) when:** Never — taxonomy consistency is essential for directory browsing and SEO.
- **Cross-reference:** The `multi-value-arrays` check verifies that multi-category listings use proper array formatting.
- **Detail on fail:** Example: `"Category is a free-form text input. Found 'Restaurant', 'restaurant', 'Food'"`
- **Remediation:** Use a select/dropdown with predefined categories:

  ```tsx
  <select name="category" required>
    <option value="">Select a category</option>
    <option value="restaurant">Restaurant</option>
    <option value="cafe">Café</option>
  </select>
  ```

Taxons: data-integrity

HTML version: https://auditbuffet.com/patterns/ab-001025