Document Retrieval System Positional Bias Correction

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Solution Overview

Problem

Document retrieval systems face challenges in accurately computing document relevance scores due to positional biases, where user selections are influenced by the position of documents in search results rather than their true relevance, leading to skewed relevance scores.

Innovation Solution

A supervised machine learning module uses user clicks and other runtime selections to learn and distinguish true document relevance from positional biases, employing a neural network to model the probability of document selection based on both document features and position, allowing for the separation of true relevance from positional effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If user clicks are used as implicit proxies for explicit relevance specifications, then the time and expense of manual relevance specification is reduced, but the accuracy of relevance scores deteriorates due to positional bias influencing user selections

Engineering Contradiction:
Improvetime for manual relevance specificationVSAvoidaccuracy of relevance scores
Core Design Contradiction:
Loss of timeVSMeasurement precision

Solution Approach 1:

The patent extracts and separates the positional bias component from the user click data. By modeling the probability of selection as a function of both relevance and position, the system isolates the positional bias effect and removes it from the relevance calculation, leaving only the true relevance signal.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a probabilistic model as an intermediary between raw user clicks and final relevance scores. This model acts as a mediator that adjusts the observed click data by accounting for positional effects, transforming biased observations into unbiased relevance estimates.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of operation

If documents are ranked by position in search results, then user selection behavior is influenced by position, but this positional influence makes it difficult to determine true document relevance

Engineering Contradiction:
Improveease of presenting search resultsVSAvoidprecision of relevance measurement
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

The patent uses feedback from observed user selection behavior across multiple positions to learn and correct for positional bias. By continuously monitoring which documents are selected at which positions and adjusting the model accordingly, the system compensates for the distorting effect of presentation order on relevance measurement.

Inventive Principle:
Principle #23Feedback

3Device complexity

If a simple relevance calculation method is used, then computational complexity is reduced, but the ability to account for positional bias and compute accurate relevance scores is compromised

Engineering Contradiction:
Improvecomplexity of relevance calculationVSAvoidaccuracy of relevance scores
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the parameters of the relevance calculation by introducing position as an additional variable and modeling the relationship between position, relevance, and user selection probability. This parameter expansion allows the system to account for positional bias while maintaining a computationally tractable probabilistic framework.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS10565265B2Accounting for positional bias in a document retrieval system using machine learning
Publication Date: 2020.02.18 SALESFORCE INC
  • US10565265B2 patent drawing
  • US10565265B2 patent drawing
  • US10565265B2 patent drawing

AI summary

A document retrieval system tracks user selections of documents from query search results and uses the selections as proxies for manual user labeling of document relevance. The system trains a model representing the significance of different document features when calculating true document relevance for users. To factor in positional biases inherent in user selections in search results, the system learns positional bias values for different search result positions, such that the positional bias values are accounted for when computing document feature features that are used to compute true document relevance.