让知识随时间自动失效,防止过时信息误导大模型输出。
Chronofy: A Temporal-Logical Decay Architecture for Information Validity in Time-Aware Retrieval-Augmented Generation
- 用时间嵌入层让事实年龄无法从表示中剥离
- 通过贝叶斯理论设定衰减系数,实现可学习的时间衰减
- 用逻辑公式判断知识时效性,确保推理链中最旧证据决定结果可信度
检索增强生成(RAG)系统依赖外部知识来支撑大语言模型输出。但现有架构忽视事实的时间来源,导致时间幻觉——看似合理却已过时的信息污染输出。昨日的临床检测结果有用,六个月前的则无意义。本文提出Chronofy,一种三层神经符号框架,实现时间逻辑衰减架构(TLDA),将时间有效性直接嵌入表示、检索和推理层。第一层在马特里什卡嵌入中保留专用时间子空间,使事实年龄不可移除;第二层在基于图的检索中引入可学习的指数衰减函数,衰减系数β_j由贝叶斯决策理论推导,近似潜过程均值回归速率的两倍;第三层使用信号时序逻辑(STL)鲁棒性函数评估知识时效性,而非模型输出置信度,并应用可能论最弱环原则,以推理链中最衰减的证据约束输出可信度。在时间知识图谱预测基准、TimE时间问答基准及领域敏感性分析中验证,显式时间衰减建模提升了检索精度,减少了时间幻觉,并在时间上下文不足时触发数据重获取。
原文摘要 · Abstract (English)
Retrieval-Augmented Generation (RAG) systems retrieve and integrate external knowledge to ground large language model (LLM) outputs. However, current RAG architectures treat all retrieved facts as equally valid regardless of temporal provenance, leading to temporal hallucination, where plausible but obsolete facts corrupt the output. A clinical lab reading from yesterday is actionable; the same reading from six months ago is noise. We present Chronofy, a three-layer neuro-symbolic framework implementing the Temporal-Logical Decay Architecture (TLDA) that embeds temporal validity directly into the representation, retrieval, and reasoning layers of RAG systems. Layer 1 reserves a dedicated temporal subspace within Matryoshka embeddings to make fact age structurally irremovable from the representation. Layer 2 integrates learnable exponential decay functions into graph-based retrieval, where the decay coefficient $β_j$ is grounded in Bayesian decision theory as an approximation of twice the latent process mean-reversion rate. Layer 3 applies Signal Temporal Logic (STL) robustness functions to evaluate the temporal validity of retrieved knowledge, not LLM output confidence, and enforces the possibilistic weakest-link principle to bound output confidence by the most decayed evidence in the reasoning chain. We evaluate Chronofy on temporal knowledge graph forecasting benchmarks, the TimE temporal QA benchmark, and a domain-specific sensitivity analysis, demonstrating that explicit temporal decay modeling improves retrieval precision, reduces temporal hallucination, and enables principled data re-acquisition triggers when temporal context is insufficient.
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