elasticsearch/docs/reference/ml
Benjamin Trent 408489310c
[ML] add zero_shot_classification task for BERT nlp models (#77799)
Zero-Shot classification allows for text classification tasks without a pre-trained collection of target labels.

This is achieved through models trained on the Multi-Genre Natural Language Inference (MNLI) dataset. This dataset pairs  text sequences with "entailment" clauses. An example could be:

"Throughout all of history, man kind has shown itself resourceful, yet astoundingly short-sighted" could have been paired with the entailment clauses: ["This example is history", "This example is sociology"...]. 

This training set combined with the attention and semantic knowledge in modern day NLP models (BERT, BART, etc.) affords a powerful tool for ad-hoc text classification.

See https://arxiv.org/abs/1909.00161 for a deeper explanation of the MNLI training and how zero-shot works. 

The zeroshot classification task is configured as follows:
```js
{
   // <snip> model configuration </snip>
  "inference_config" : {
    "zero_shot_classification": {
      "classification_labels": ["entailment", "neutral", "contradiction"], // <1>
      "labels": ["sad", "glad", "mad", "rad"], // <2>
      "multi_label": false, // <3>
      "hypothesis_template": "This example is {}.", // <4>
      "tokenization": { /*<snip> tokenization configuration </snip>*/}
    }
  }
}
```
* <1> For all zero_shot models, there returns 3 particular labels when classification the target sequence. "entailment" is the positive case, "neutral" the case where the sequence isn't positive or negative, and "contradiction" is the negative case
* <2> This is an optional parameter for the default zero_shot labels to attempt to classify
* <3> When returning the probabilities, should the results assume there is only one true label or multiple true labels
* <4> The hypothesis template when tokenizing the labels. When combining with `sad` the sequence looks like `This example is sad.`

For inference in a pipeline one may provide label updates:
```js
{
  //<snip> pipeline definition </snip>
  "processors": [
    //<snip> other processors </snip>
    {
      "inference": {
        // <snip> general configuration </snip>
        "inference_config": {
          "zero_shot_classification": {
             "labels": ["humanities", "science", "mathematics", "technology"], // <1>
             "multi_label": true // <2>
          }
        }
      }
    }
    //<snip> other processors </snip>
  ]
}
```
* <1> The `labels` we care about, these replace the default ones if they exist. 
* <2> Should the results allow multiple true labels

Similarly one may provide label changes against the `_infer` endpoint
```js
{
   "docs":[{ "text_field": "This is a very happy person"}],
   "inference_config":{"zero_shot_classification":{"labels": ["glad", "sad", "bad", "rad"], "multi_label": false}}
}
```
2021-09-28 09:38:23 -04:00
..
anomaly-detection [ML] add new default char filter first_line_with_letters for machine learning categorization (#77457) 2021-09-09 10:09:57 -04:00
df-analytics/apis [ML] add zero_shot_classification task for BERT nlp models (#77799) 2021-09-28 09:38:23 -04:00
images [DOCS] Adds anomaly job health alert type docs (#76659) 2021-08-30 16:11:34 +02:00
ml-shared.asciidoc [ML] add zero_shot_classification task for BERT nlp models (#77799) 2021-09-28 09:38:23 -04:00