Intent Transformers

Intent Transformers are a pluggable mechanism in OVOS that allow you to enrich or transform intent data after an intent is matched by an engine (Padatious, Adapt, etc.), but before it is passed to the skill handler.

This is useful for:

• Named Entity Recognition (NER)
• Keyword extraction
• Slot filling
• Contextual enrichment

Transformers operate on IntentHandlerMatch or PipelineMatch objects and are executed in order of priority. They enable complex processing pipelines without requiring every skill to reimplement entity logic.

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Default Transformers

In a standard OVOS installation, the following plugins are installed and enabled by default:

Plugin	Description	Priority
ovos-keyword-template-matcher	Extracts values from {placeholder}-style intent templates	1
ovos-ahocorasick-ner-plugin	Performs NER using Aho-Corasick keyword matching based on registered entities from skill templates	5

These are not built into core, but are bundled in standard OVOS setups and configured via intent_transformers in your configuration file.

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Configuration

To enable or disable specific transformers, modify your mycroft.conf:

"intent_transformers": {
  "ovos-keyword-template-matcher": {
    "active": true
  },
  "ovos-ahocorasick-ner-plugin": {
    "active": false
  }
}

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How It Works

Example Workflow

1. An utterance matches an intent via Padatious, Adapt, or another engine.
2. The matched intent is passed to the IntentTransformersService.
3. Each registered transformer plugin runs its transform() method.
4. Extracted entities are injected into the intent’s match_data.
5. The updated match_data is passed to the skill via the Message object.

Skill Access

Entities extracted by transformers are made available to your skill in the message.data dictionary:

location = message.data.get("location")
person = message.data.get("person")

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Default Plugins

ovos-ahocorasick-ner-plugin

This plugin builds a per-skill Aho-Corasick automaton using keywords explicitly provided by the developer via registered entities.

❗ It will only match keywords that the skill developer has accounted for

It does not use external data or extract entities generically.

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ovos-keyword-template-matcher

This plugin parses registered intent templates like:

what's the weather in {location}

It uses the template structure to extract {location} directly from the utterance.

If the user says "what's the weather in Tokyo", the plugin will populate:

match_data = {
  "location": "Tokyo"
}

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Writing Your Own Intent Transformer

To create a custom transformer:

from ovos_plugin_manager.templates.transformers import IntentTransformer

class MyCustomTransformer(IntentTransformer):
    def __init__(self, config=None):
        super().__init__("my-transformer", priority=10, config=config)

    def transform(self, intent):
        # Modify intent.match_data here
        return intent