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Ontology-driven personalized information retrieval for XML documents

cs.IR cs.LG Ounnaci Iddir, Ahmed-ouamer Rachid, Tai Dinh · Mar 22, 2026

This paper addresses personalized information retrieval for XML documents by representing users, queries, and documents as weighted concept vectors derived from a domain ontology. The core idea is a hierarchical weighting scheme that favors specific (deeper) ontology concepts combined with a dynamic profile update mechanism that reinforces concepts based on user interactions. The work targets the limitation of traditional keyword-based systems that return identical results regardless of user knowledge or preferences.

This paper addresses the challenge of improving information retrieval from semi-structured eXtensible Markup Language (XML) documents. Traditional information retrieval systems (IRS) often overlook user-specific needs and return identical results for the same query, despite differences in users' knowledge, preferences, and objectives. We integrate external semantic resources, namely a domain ontology and user profiles, into the retrieval process. Documents, queries, and user profiles are represented as vectors of weighted concepts. The ontology applies a concept-weighting mechanism that emphasizes highly specific concepts, as lower-level nodes in the hierarchy provide more precise and targeted information. Relevance is assessed using semantic similarity measures that capture conceptual relationships beyond keyword matching, enabling personalized and fine-grained matching among user profiles, queries, and documents. Experimental results show that combining ontologies with user profiles improves retrieval effectiveness, achieving higher precision and recall than keyword-based approaches. Overall, the proposed framework enhances the relevance and adaptability of XML search results, supporting more user-centered retrieval.

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One Model, Two Markets: Bid-Aware Generative Recommendation

cs.IR cs.AI cs.GT Yanchen Jiang, Zhe Feng, Christopher P. Mah et al. · Mar 23, 2026

Generative recommender systems like TIGER excel at semantic retrieval but ignore the economic realities of monetization via sponsored content. This paper proposes GEM-Rec, a unified framework that augments semantic IDs with control tokens (<ORG>, <AD>) to factorize slot allocation from item generation, and introduces Bid-Aware Decoding to inject real-time auction bids into inference. The work bridges the gap between generative recommendation and computational advertising, offering theoretical guarantees like allocative monotonicity while allowing dynamic trade-offs between user relevance and platform revenue.

Generative Recommender Systems using semantic ids, such as TIGER (Rajput et al., 2023), have emerged as a widely adopted competitive paradigm in sequential recommendation. However, existing architectures are designed solely for semantic retrieval and do not address concerns such as monetization via ad revenue and incorporation of bids for commercial retrieval. We propose GEM-Rec, a unified framework that integrates commercial relevance and monetization objectives directly into the generative sequence. We introduce control tokens to decouple the decision of whether to show an ad from which item to show. This allows the model to learn valid placement patterns directly from interaction logs, which inherently reflect past successful ad placements. Complementing this, we devise a Bid-Aware Decoding mechanism that handles real-time pricing, injecting bids directly into the inference process to steer the generation toward high-value items. We prove that this approach guarantees allocation monotonicity, ensuring that higher bids weakly increase an ad's likelihood of being shown without requiring model retraining. Experiments demonstrate that GEM-Rec allows platforms to dynamically optimize for semantic relevance and platform revenue.

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AgenticRec: End-to-End Tool-Integrated Policy Optimization for Ranking-Oriented Recommender Agents

cs.IR cs.AI Tianyi Li, Zixuan Wang, Guidong Lei et al. · Mar 23, 2026

AgenticRec attacks a key gap in LLM-based recommenders: existing agents rely on frozen reasoning chains and cannot learn from ranking feedback to refine tool use. The paper proposes a two-stage training framework that combines ReAct-style tool invocation with list-wise Group Relative Policy Optimization (GRPO) and Progressive Preference Refinement (PPR) for hard-negative mining. The work matters because it demonstrates that end-to-end reinforcement learning can align multi-step tool use with ranking objectives, moving beyond prompt-engineered agent workflows.

Recommender agents built on Large Language Models offer a promising paradigm for recommendation. However, existing recommender agents typically suffer from a disconnect between intermediate reasoning and final ranking feedback, and are unable to capture fine-grained preferences. To address this, we present AgenticRec, a ranking-oriented agentic recommendation framework that optimizes the entire decision-making trajectory (including intermediate reasoning, tool invocation, and final ranking list generation) under sparse implicit feedback. Our approach makes three key contributions. First, we design a suite of recommendation-specific tools integrated into a ReAct loop to support evidence-grounded reasoning. Second, we propose theoretically unbiased List-Wise Group Relative Policy Optimization (list-wise GRPO) to maximize ranking utility, ensuring accurate credit assignment for complex tool-use trajectories. Third, we introduce Progressive Preference Refinement (PPR) to resolve fine-grained preference ambiguities. By mining hard negatives from ranking violations and applying bidirectional preference alignment, PPR minimizes the convex upper bound of pairwise ranking errors. Experiments on benchmarks confirm that AgenticRec significantly outperforms baselines, validating the necessity of unifying reasoning, tool use, and ranking optimization.

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Toward a Theory of Hierarchical Memory for Language Agents

cs.IR cs.AI cs.IT Yashar Talebirad, Ali Parsaee, Csongor Y. Szepesvari et al. · Mar 23, 2026

This paper tackles the lack of shared formalism for comparing hierarchical memory systems in language agents. It proposes a unifying theory based on three operators: extraction (α) that maps raw data to atomic units, coarsening (C = (π, ρ)) that partitions and summarizes units, and traversal (τ) that selects content under a token budget. The core insight is the self-sufficiency spectrum of representatives ρ, which constrains viable retrieval strategies—an observation the authors call the coarsening-traversal (C–T) coupling.

Many recent long-context and agentic systems address context-length limitations by adding hierarchical memory: they extract atomic units from raw data, build multi-level representatives by grouping and compression, and traverse this structure to retrieve content under a token budget. Despite recurring implementations, there is no shared formalism for comparing design choices. We propose a unifying theory in terms of three operators. Extraction ($\alpha$) maps raw data to atomic information units; coarsening ($C = (\pi, \rho)$) partitions units and assigns a representative to each group; and traversal ($\tau$) selects which units to include in context given a query and budget. We identify a self-sufficiency spectrum for the representative function $\rho$ and show how it constrains viable retrieval strategies (a coarsening-traversal coupling). Finally, we instantiate the decomposition on eleven existing systems spanning document hierarchies, conversational memory, and agent execution traces, showcasing its generality.

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When Documents Disagree: Measuring Institutional Variation in Transplant Guidance with Retrieval-Augmented Language Models

cs.IR cs.AI Yubo Li, Ramayya Krishnan, Rema Padman · Mar 23, 2026

This paper introduces a scalable framework to measure institutional variation in solid-organ transplant patient education materials using retrieval-augmented generation (RAG). The authors ground 1,115 patient questions across 102 handbooks from 23 U.S. centers, then classify answer pairs into a five-label taxonomy (Absent, Consistent, Complementary, Divergent, Contradictory). The work exposes critical information gaps: 96.2% of question-handbook pairs miss relevant content, and 20.8% of non-absent pairs show clinically meaningful divergence, with reproductive health nearly absent (95.1%) across all materials.

Patient education materials for solid-organ transplantation vary substantially across U.S. centers, yet no systematic method exists to quantify this heterogeneity at scale. We introduce a framework that grounds the same patient questions in different centers' handbooks using retrieval-augmented language models and compares the resulting answers using a five-label consistency taxonomy. Applied to 102 handbooks from 23 centers and 1,115 benchmark questions, the framework quantifies heterogeneity across four dimensions: question, topic, organ, and center. We find that 20.8% of non-absent pairwise comparisons exhibit clinically meaningful divergence, concentrated in condition monitoring and lifestyle topics. Coverage gaps are even more prominent: 96.2% of question-handbook pairs miss relevant content, with reproductive health at 95.1% absence. Center-level divergence profiles are stable and interpretable, where heterogeneity reflects systematic institutional differences, likely due to patient diversity. These findings expose an information gap in transplant patient education materials, with document-grounded medical question answering highlighting opportunities for content improvement.

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COINBench: Moving Beyond Individual Perspectives to Collective Intent Understanding

cs.IR cs.AI Xiaozhe Li, Tianyi Lyu, Siyi Yang et al. · Mar 22, 2026

Understanding collective human intent from noisy, conflicting public discourse represents a frontier AI challenge that extends beyond individual instruction-following. This paper introduces COIN-Bench, a live-updating benchmark comprising 200k+ real consumer discussions across 1,400+ products, which operationalizes an Active Probing Paradigm requiring LLMs to act as meta-analysts and reconstruct chaotic feedback into structured questionnaires. The work matters because it shifts evaluation from transactional action prediction to hierarchical consensus synthesis, testing whether models can resolve contradictions and infer latent trends from swarm-like intelligence.

Understanding human intent is a high-level cognitive challenge for Large Language Models (LLMs), requiring sophisticated reasoning over noisy, conflicting, and non-linear discourse. While LLMs excel at following individual instructions, their ability to distill Collective Intent - the process of extracting consensus, resolving contradictions, and inferring latent trends from multi-source public discussions - remains largely unexplored. To bridge this gap, we introduce COIN-BENCH, a dynamic, real-world, live-updating benchmark specifically designed to evaluate LLMs on collective intent understanding within the consumer domain. Unlike traditional benchmarks that focus on transactional outcomes, COIN-BENCH operationalizes intent as a hierarchical cognitive structure, ranging from explicit scenarios to deep causal reasoning. We implement a robust evaluation pipeline that combines a rule-based method with an LLM-as-the-Judge approach. This framework incorporates COIN-TREE for hierarchical cognitive structuring and retrieval-augmented verification (COIN-RAG) to ensure expert-level precision in analyzing raw, collective human discussions. An extensive evaluation of 20 state-of-the-art LLMs across four dimensions - depth, breadth, informativeness, and correctness - reveals that while current models can handle surface-level aggregation, they still struggle with the analytical depth required for complex intent synthesis. COIN-BENCH establishes a new standard for advancing LLMs from passive instruction followers to expert-level analytical agents capable of deciphering the collective voice of the real world. See our project page on COIN-BENCH.

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ECI: Effective Contrastive Information to Evaluate Hard-Negatives

cs.IR cs.AI Aarush Sinha, Rahul Seetharaman, Aman Bansal · Mar 22, 2026

This paper introduces ECI (Effective Contrastive Information), a training-free metric for evaluating hard-negative mining strategies in dense retrieval. The core idea is to leverage the logarithmic InfoNCE bound on mutual information combined with a harmonic mean of signal (hardness) and safety (margin) to predict downstream retrieval quality without expensive fine-tuning. The proposed metric addresses a real pain point in retrieval research: practitioners currently must run end-to-end ablation studies to evaluate negative sampling strategies, which is computationally wasteful.

Hard negatives play a critical role in training and fine-tuning dense retrieval models, as they are semantically similar to positive documents yet non-relevant, and correctly distinguishing them is essential for improving retrieval accuracy. However, identifying effective hard negatives typically requires extensive ablation studies involving repeated fine-tuning with different negative sampling strategies and hyperparameters, resulting in substantial computational cost. In this paper, we introduce ECI: Effective Contrastive Information , a theoretically grounded metric grounded in Information Theory and Information Retrieval principles that enables practitioners to assess the quality of hard negatives prior to model fine-tuning. ECI evaluates negatives by optimizing the trade-off between Information Capacity the logarithmic bound on mutual information determined by set size and Discriminative Efficiency, a harmonic balance of Signal Magnitude (Hardness) and Safety (Max-Margin). Unlike heuristic approaches, ECI strictly penalizes unsafe, false-positive negatives prevalent in generative methods. We evaluate ECI across hard-negative sets mined or generated using BM25, cross-encoders, and large language models. Our results demonstrate that ECI accurately predicts downstream retrieval performance, identifying that hybrid strategies (BM25+Cross-Encoder) offer the optimal balance of volume and reliability, significantly reducing the need for costly end-to-end ablation studies.

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Compiling Autoregressive LLM Control into Policy-Exact Parallel Inference for Hierarchical RAG

cs.CL cs.IR Zehao Lin, Qianfeng Shen, Xixuan Hao et al. · Oct 22, 2026

Large language models increasingly act as controllers in structured decision pipelines, yet their decisions are still executed by autoregressive text decoding. Hierarchical RAG is one such setting: at each frontier of a document tree, an LLM commits to $b$ of $k$ sections under an input-dependent action grammar, executed as either failure-prone free-form JSON or reliable but strictly serial grammar-constrained generation. We show that this serialization is unnecessary for bounded-horizon control: the reachable future forms a shallow action-prefix tree, which we compile --- one root prefill plus one tree-causal probe evaluate every prefix-conditioned action distribution with serial decoding's tokens, positions, and causal ancestry. A prefix-state lemma makes compiled control policy-exact in exact arithmetic: the same policy with a two-forward critical path and zero output tokens. One further probe pass certifies the exact order-marginalized MAP set. Across four document-disjoint splits and two scales on the primary MetaX device, compiled control matches the serial policy on $84$--$89\%$ of questions --- every instrumented divergence a floating-point near-tie --- and cuts control latency by $35$--$47\%$ versus token-wise serial decoding and $6$--$7\%$ versus an idealized chunked engine; an H800 repetition preserves the ordering.

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HEM-Med: A Hierarchical Agentic Memory Framework for Safe Multi-Center Medication Recommendation

cs.AI cs.IR Min Xiao, Jin Li, Shoujin Wang et al. · Oct 14, 2026

Medication recommendation (MR) is critical for clinical decision support. While existing MR methods are mostly designed for single-center learning, where only one independent hospital is involved, multi-center MR with hospitals of different scales has become increasingly demanding in practice. In multi center settings, abundant data from large medical centers can improve recommendation performance for low-resource centers. Despite a few preliminary attempts on this task, two critical gaps remain. Gap 1: Existing multi-center methods fail to disentangle transferable cross-hospital clinical experience from hospital-specific prescribing patterns, limiting clinical feasibility and physician acceptance. Gap 2: They commonly overlook multi label safety constraints of MR, including drug-drug interaction risks and local formulary feasibility, which are essential for safe real-world deployment. To address these gaps, we propose HEM-Med, a novel hierarchical agentic memory framework for multi-center MR. To address Gap 1, we design a disentangled hierarchical memory module that builds patient-level medication context attribution records and disentangles them into cross hospital experience memory and hospital-specific residual memory. To address Gap 2, we introduce a safety-aware medication set generation module, which integrates dual-level experience retrieval with safety-aware set decoding to produce clinically relevant, safer, and locally adaptive medication recommendations. Experiments on a real-world multi-center eICU dataset show that HEM-Med outperforms representative transfer learning, LLM-based, and MR baselines in terms of both recommendation accuracy and safety.

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