Valeria Secchini | Searcharxiv

arXiv2026

RAGEAR: Retrieval-Augmented Graph-Enhanced Academic Recommender

We present RAGEAR (Retrieval-Augmented Graph-Enhanced Academic Recommender), a neurosymbolic recommender system for academic course recommendation. RAGEAR combines dense retrieval over full lecture transcripts with a symbolic Knowledge Graph modelling courses, lessons, transcript chunks, credits, study plans, and curricular information. The Knowledge Graph supports symbolic filtering and contextualisation based on structured constraints, such as credits, academic disciplines, study plans, and prerequisites. Unlike metadata-based approaches, it exploits fine-grained instructional content by retrieving transcript chunks semantically aligned with a student's query. The main contribution is a graph-aware aggregation function that propagates chunk-level evidence to course-level recommendations. The score combines three factors: the share of retrieved similarity associated with a course, the rank-based strength of its relevant chunks, and the distribution of evidence across lessons. We evaluate RAGEAR on 152 student-like queries through a human evaluation sample and a large-scale LLM-based relevance assessment. Results show that lecture transcripts improve over metadata-only retrieval, and that RAGEAR further improves ranking quality over a transcript-based normalized SumP baseline, especially for top-ranked recommendations.

cs.IR↗

arXiv2025

Avoiding Overfitting in Variable-Order Markov Models: a Cross-Validation Approach

Higher$\text{-}$order Markov chain models are widely used to represent agent transitions in dynamic systems, such as passengers in transport networks. They capture transitions in complex systems by considering not only the current state but also the path of previously visited states. For example, the likelihood of train passengers traveling from Paris (current state) to Rome could increase significantly if their journey originated in Italy (prior state). Although this approach provides a more faithful representation of the system than first$\text{-}$order models, we find that commonly used methods$-$relying on Kullback$\text{-}$Leibler divergence$-$frequently overfit the data, mistaking fluctuations for higher$\text{-}$order dependencies and undermining forecasts and resource allocation. Here, we introduce DIVOP (Detection of Informative Variable$\text{-}$Order Paths), an algorithm that employs cross$\text{-}$validation to robustly distinguish meaningful higher$\text{-}$order dependencies from noise. In both synthetic and real$\text{-}$world datasets, DIVOP outperforms two state$\text{-}$of$\text{-}$the$\text{-}$art algorithms by achieving higher precision, recall, and sparser representations of the underlying dynamics. When applied to global corporate ownership data, DIVOP reveals that tax havens appear in 82$\%$ of all significant higher$\text{-}$order dependencies, underscoring their outsized influence in corporate networks. By mitigating overfitting, DIVOP enables more reliable multi$\text{-}$step predictions and decision$\text{-}$making, paving the way toward deeper insights into the hidden structures that drive modern interconnected systems.

physics.soc-ph↗