Skip to main content
Semantic enrichment adds contextual attributes to PII placeholders, helping translation systems maintain grammatical correctness across languages.

​
Why Semantic Attributes?

Many languages have grammatical gender agreement. Without knowing the gender of a person, translation quality suffers: 
// Without semantic enrichment
Input:  "Thank <PII type="PERSON" id="1"/> for the help."
German: "Danke <PII type="PERSON" id="1"/> für die Hilfe."

// With semantic enrichment
Input:  "Thank <PII type="PERSON" gender="female" id="1"/> for the help."
German: "Danke ihr für die Hilfe."  // Correct feminine pronoun

​
Enable Semantic Enrichment

import { createAnonymizer } from 'rehydra';

const anonymizer = createAnonymizer({
  ner: { mode: 'quantized' },
  semantic: { 
    enabled: true,
    onStatus: (status) => console.log(status),
  }
});

await anonymizer.initialize();

const result = await anonymizer.anonymize('Hello Maria Schmidt from Berlin!');
console.log(result.anonymizedText);
// "Hello <PII type="PERSON" gender="female" id="1"/> from <PII type="LOCATION" scope="city" id="2"/>!"

​
Semantic Attributes

​
Person Gender

Attribute ValueMeaningExample Names
gender="male"Masculine nameJohn, Michael, Hans
gender="female"Feminine nameMaria, Sarah, Anna
gender="neutral"Ambiguous/unknownAlex, Jordan, Sam

​
Location Scope

Attribute ValueMeaningExamples
scope="city"City/townBerlin, Paris, Tokyo
scope="country"CountryGermany, France, Japan
scope="region"Region/stateBavaria, California, Hokkaido

​
Semantic Data

Semantic enrichment uses lookup databases (~12 MB total):
  • Name database: First names with gender associations
  • Location database: Cities, countries, regions with classifications

​
First-Use Download

const anonymizer = createAnonymizer({
  semantic: { 
    enabled: true,
    autoDownload: true,  // Default: auto-download if not cached
    onDownloadProgress: (progress) => {
      console.log(`${progress.file}: ${progress.percent}%`);
    }
  }
});

​
Manual Data Management

import { 
  isSemanticDataDownloaded,
  downloadSemanticData,
  clearSemanticDataCache 
} from 'rehydra';

// Check if data is cached
const hasData = await isSemanticDataDownloaded();

// Pre-download
await downloadSemanticData((progress) => {
  console.log(`${progress.file}: ${progress.percent}%`);
});

// Clear cache
await clearSemanticDataCache();

​
Title Extraction

When semantic enrichment is enabled, honorific titles are extracted and kept visible: 
const result = await anonymizer.anonymize('Contact Dr. Maria Schmidt');
// "Contact Dr. <PII type="PERSON" gender="female" id="1"/>"
Supported titles:
  • Academic: Dr., Prof., PhD
  • Honorific: Mr., Mrs., Ms., Miss
  • Professional: Rev., Hon.
  • German: Herr, Frau, Dr.
  • French: M., Mme., Mlle.
  • And many more…
Titles remain visible because they’re often important for translation and don’t reveal the person’s identity on their own.

​
Locale Hints

Improve detection accuracy with locale hints: 
const result = await anonymizer.anonymize(
  'Bonjour Jean-Pierre de Lyon!',
  'fr-FR'  // French locale
);
The locale helps with:
  • Name gender inference (culture-specific names)
  • Title recognition (Mr. vs Herr vs M.)

​
Configuration Options

const anonymizer = createAnonymizer({
  semantic: {
    enabled: true,
    autoDownload: true,
    onStatus: (status) => console.log(status),
    onDownloadProgress: (progress) => {
      console.log(`${progress.file}: ${progress.percent}%`);
    }
  },
  defaultPolicy: {
    enableSemanticMasking: true,  // Enable in policy (auto-set when semantic.enabled)
  }
});

​
Cache Locations

Semantic data is cached locally:

​
Node.js

PlatformLocation
macOS~/Library/Caches/rehydra/semantic-data/
Linux~/.cache/rehydra/semantic-data/
Windows%LOCALAPPDATA%/rehydra/semantic-data/

​
Browser

Uses IndexedDB for cross-session persistence.

​
Use Cases

German, French, Spanish, and many other languages have grammatical gender. Semantic attributes help MT systems:
EN: "Please contact <PII gender="female"/> for assistance."
DE: "Bitte kontaktieren Sie sie für Unterstützung."
Different location types use different prepositions:
"I'm in Berlin" (city) → "Ich bin in Berlin"
"I'm in Germany" (country) → "Ich bin in Deutschland"
The scope attribute helps translation systems choose correctly.
Beyond translation, semantic attributes enable:
  • Gender-aware text generation
  • Location-based content filtering
  • Name normalization

​
Next Steps

Browser Usage

Using semantic enrichment in browsers

Sessions & Storage

Persist enriched PII maps