Surrogate Model for Interpretable NLP Classification

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Solution Overview

Problem

Modern natural language processing (NLP) systems, particularly those using deep learning, operate in a 'black box' fashion, making it difficult to interpret how they arrive at decisions, which is a concern for transparency and accountability in applications like financial institutions.

Innovation Solution

The proposed solution involves creating an interpretable surrogate model by scoring input data using an NLP model, generating a balanced sample of observations, and training a surrogate model to identify the most influential tokens. These tokens provide insight into the original NLP model's decision-making process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high-dimensional contextual embedding is used to improve NLP model accuracy, then classification accuracy is improved, but model interpretability deteriorates

Engineering Contradiction:
Improveclassification accuracyVSAvoidmodel interpretability
Core Design Contradiction:
Measurement precisionVSLoss of information

Solution Approach 1:

The patent creates a surrogate model that copies the predictive behavior of the complex NLP model but uses simple, interpretable features (bag-of-words) instead of high-dimensional contextual embeddings. This surrogate model replicates the classification accuracy while maintaining feature interpretability, allowing users to understand which words drive predictions without needing to interpret the black-box embedding space.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The surrogate model acts as an intermediary between the complex NLP model and the user. It translates the opaque high-dimensional embedding decisions into interpretable word-level explanations, serving as a mediator that preserves predictive accuracy while providing transparency about which tokens influenced the output.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Measurement precision

If complex deep learning networks are used to enhance NLP capabilities, then processing accuracy is improved, but device complexity increases

Engineering Contradiction:
Improveprocessing accuracyVSAvoidmodel complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential predictive information from the complex NLP model by training a surrogate model on bag-of-words features. This extraction process isolates the meaningful patterns without requiring the complexity of the original deep learning architecture, achieving accuracy while reducing model complexity.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The surrogate model serves as a simpler, more affordable alternative to the complex NLP model. It uses basic machine learning algorithms and simple features rather than expensive high-dimensional embeddings, providing a cost-effective way to achieve interpretability without sacrificing predictive performance.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Productivity

If embedding transformation is applied to convert text to numerical vectors, then model prediction capability is improved, but ease of interpretation deteriorates

Engineering Contradiction:
Improveprediction capabilityVSAvoidease of interpretation
Core Design Contradiction:
ProductivityVSEase of operation

Solution Approach 1:

Instead of trying to interpret the high-dimensional embedding space directly, the patent inverts the approach by training a surrogate model that uses simple, human-readable word features. This inversion allows the system to maintain sophisticated prediction capability through the NLP model while providing easy interpretation through the surrogate model's simple feature space.

Inventive Principle:
Principle #13The other way round (Inversion)

Data Source

PatentUS12288029B2Systems and methods for flexible regularized distillation of natural language processing models to facilitate interpretation
Publication Date: 2025.04.29 WELLS FARGO BANK NA
  • US12288029B2 patent drawing
  • US12288029B2 patent drawing
  • US12288029B2 patent drawing

AI summary

Systems, apparatuses, methods, and computer program products are disclosed for distillation of a natural language processing model. An example method includes receiving, by communications circuitry, a set of text data comprising a set of observations and predicting, by processing circuitry and using the NLP model, classifications for each observation in the text data. The example method further includes generating, by model training engine, a balanced sampled data structure based on the predicted classifications for each observation in the text data and training, by the model training engine, a surrogate model using the balanced sampled data structure. The example method further includes identifying, by an interpreter and from the surrogate model, a set of most-influential tokens in the text data.