Generalizing Information Theory: Uncertainty Reduction through Arbitrary Loss Functions

核心概念

Entropy and information can be generalized beyond Shannon's original framework by considering arbitrary loss functions to quantify uncertainty reduction, rather than just message length. This provides a unified perspective on various information-theoretic quantities.

摘要

The paper presents a generalized framework for defining entropy and information measures, going beyond Shannon's original formulation based on message length. The key ideas are:

1. Uncertainty can be quantified through the reduction in optimal loss when moving from no knowledge to full knowledge about a random variable X, using an arbitrary loss function l(x, a) defined on the random variable X and actions a.

2. This uncertainty reduction is formalized as U{∅,Ω}→σ(X)(X), where {∅, Ω} represents no knowledge and σ(X) represents full knowledge about X.

3. Entropy H(X) is then defined as the uncertainty reduction from no knowledge to full knowledge. Conditional entropy H(X|σ) and information I(X; σ) are defined as uncertainty reductions to partial knowledge represented by a sub-σ-algebra σ.

4. This framework generalizes Shannon entropy and information, which correspond to the case where l is the log loss. Other examples include variance for square error loss, and Bregman information for Bregman divergences.

5. In the continuous case, H(X) and H(X|Y) can be infinite, reflecting the ability to store arbitrary amounts of information. However, I(X; Y) and I(X; Y|Z) can still be finite, quantifying uncertainty reduction to partial knowledge.

6. The framework also allows incorporating uncertainty about the true distribution pX, by considering a set Γ of candidate distributions and the uncertainty between Γ and pX.

Overall, the paper provides a unifying perspective on information-theoretic quantities, showing how they can be generalized beyond Shannon's original coding-theoretic motivation.

统计

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引用

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从中提取的关键见解

On the Structure of Information

by Sebastian Go... 在 arxiv.org 10-01-2024

https://arxiv.org/pdf/2409.20331.pdf

更深入的查询

1. How could the proposed framework be applied to develop new information-theoretic measures tailored to specific applications or domains?

The proposed framework generalizes the concept of information and uncertainty reduction by allowing for arbitrary loss functions. This flexibility opens avenues for developing new information-theoretic measures that can be specifically tailored to various applications or domains. For instance, in fields such as finance, healthcare, or machine learning, practitioners often deal with unique types of data and decision-making scenarios that may not align well with traditional measures like Shannon entropy or mutual information.
By selecting appropriate loss functions that reflect the specific costs or benefits associated with decisions in these domains, researchers can derive new measures of information that capture the nuances of uncertainty in those contexts. For example, in healthcare, a loss function could be designed to prioritize minimizing false negatives over false positives, leading to a measure of information that emphasizes the importance of correctly identifying patients at risk. Similarly, in machine learning, loss functions that account for class imbalance can yield information measures that better reflect the predictive performance of models on minority classes.
Moreover, the framework's reliance on sub-σ-algebras allows for a structured approach to incorporate prior knowledge and contextual information, enabling the development of measures that are not only mathematically robust but also practically relevant. This adaptability can lead to the creation of hybrid measures that combine elements from different domains, fostering interdisciplinary research and innovation.

2. What are the implications of allowing the loss function l to be arbitrary, beyond the examples considered in the paper? Are there any fundamental limitations or challenges that arise?

Allowing the loss function ( l ) to be arbitrary introduces significant flexibility in modeling uncertainty and information. However, this freedom also brings forth several implications, limitations, and challenges.
One major implication is the potential for overfitting to specific contexts or datasets. When the loss function is tailored too closely to a particular application, it may not generalize well to other scenarios, leading to measures of information that are not broadly applicable. This raises concerns about the robustness and reliability of the derived information measures, as they may become sensitive to the choice of loss function.
Additionally, the choice of an arbitrary loss function can complicate the interpretation of the resulting information measures. Different loss functions can yield vastly different insights into uncertainty and information, making it challenging to compare results across studies or applications. This variability necessitates a careful consideration of the implications of the chosen loss function, as it can influence the conclusions drawn from the analysis.
Furthermore, there are fundamental challenges related to the mathematical properties of the loss functions. For instance, not all loss functions may satisfy desirable properties such as convexity or continuity, which are often crucial for ensuring the existence of optimal solutions and the stability of the derived measures. This could lead to difficulties in optimization and interpretation, particularly in high-dimensional spaces.

3. How might the ideas of incorporating uncertainty about the true distribution pX be further developed, and what are the connections to concepts like the maximum entropy principle and robust Bayesian inference?

Incorporating uncertainty about the true distribution ( p_X ) can be further developed by exploring the interplay between different distributions and their associated uncertainties. One approach is to model the uncertainty in ( p_X ) using a family of distributions ( \Gamma ), which can represent prior beliefs or estimates based on available data. This leads to a richer framework for understanding how uncertainty propagates through the decision-making process.
The connection to the maximum entropy principle is particularly relevant here. The maximum entropy principle posits that, given a set of constraints, the probability distribution that best represents the current state of knowledge is the one with the maximum entropy. By integrating this principle into the framework, one can derive distributions that not only reflect the available information but also account for the uncertainty inherent in the estimation of ( p_X ). This can lead to more robust decision-making strategies that are less sensitive to specific assumptions about the underlying distribution.
Robust Bayesian inference also plays a crucial role in this context. By considering the worst-case scenarios or the most uncertain distributions within the family ( \Gamma ), one can develop robust Bayesian methods that provide credible intervals or bounds on the estimates of ( p_X ). This approach allows for a systematic way to incorporate uncertainty into the analysis, leading to more reliable conclusions and decisions.
Overall, the integration of uncertainty about ( p_X ) with concepts like maximum entropy and robust Bayesian inference can enhance the framework's applicability across various domains, providing a comprehensive understanding of information and uncertainty in complex decision-making environments.