We present an extension of Triangolazioni (a Cultural Heritage webapp) to enrich curated content with context-dependent, external information provided by Large Language Models (LLMs) within a loosely-coupled architecture agnostic to the LLM. The system supports context-dependent information search and presentation within an architecture agnostic to the exploited LLM.

Fairness represents a crucial aspect of recommender systems. While past research has focused on improving both item and group fairness, these efforts have relied primarily on offline evaluation methods. However, fairness-aware recommender systems face a critical gap between offline algorithmic evaluation and users’ online perceptions. In this paper, we investigate relationships between offline and perceived fairness measurements, and how group item fairness post-hoc interventions impact group user fairness across demographic segments. Our findings reveal misalignments between offline fairness evaluation and users’ perceptions of fairness. Moreover, post-hoc interventions to enhance offline group item fairness produced unexpected effects across different user groups, particularly regarding age and education level. This calls for the need to incorporate user studies into the evaluation of algorithms for fairness-aware recommender systems to ensure equitable outcomes. Our source code is publicly available at https://bit.ly/483TssZ.

In an era where personalization technologies increasingly shape human decision-making, integrating sustainability and social good into user-adaptive systems has become an essential challenge. Building on recent advances in User Modeling, Personalization, and Adaptive Systems, this workshop aims to consolidate a research agenda focused on how personalization can support sustainable behaviors, ethical decision-making, inclusion, and positive societal impact. Personalized and adaptive systems influence users’ choices across many contexts—health, mobility, education, media consumption, and more. Their role in shaping long-term behavioral change positions them as key technologies for supporting the UN Sustainable Development Goals and broader sustainability initiatives. This workshop provides an interdisciplinary venue to explore theoretical, methodological, and practical advances at the intersection of sustainability, personalization, and adaptive systems. Through presentations, discussions, and interactive sessions, the workshop aims to stimulate knowledge exchange and collaboration for developing sustainable personalized systems.

Multimodal item representations are widely used in modern recommender systems to capture various aspects of items. However, the high dimensionality of these representations poses challenges in terms of computational efficiency and resource usage. In this paper, we propose a fusion method, named MDR , based on attention bottlenecks to obtain condensed multimodal item representations. Our approach, intersecting dimensionality reduction and information fusion, leverages a Transformer autoencoder architecture to learn a compact item representation that preserves the salient information from the original high-dimensional features. We evaluate the impact of the condensed representations on the recommendation performance and resource consumption of a set of recommendation algorithms using the Cornac framework. Experiments on four datasets show that the condensed item representations produced by our fusion method enable the recommender algorithms to achieve comparable or even improved recommendation performance compared to the original, high-dimensional representations. Moreover, using the condensed representations significantly reduces training time, RAM Memory usage, and GPU utilization. These findings highlight the potential of our approach to enhance the efficiency and sustainability of multimodal recommender systems without compromising their effectiveness.

Travel experiences can challenge individuals with Autism Spectrum Disorder (ASD) before embarking on a trip, because of the complexity of planning, but also during the trip, due to sensory overstimulation while visiting places. Artificial Intelligence (AI) could help overcome some obstacles. However, it might represent a barrier for people with mid-functioning autism if their needs for assistance are not considered when designing tourism applications. Moreover, most trip planners fully control the generation of solutions, undermining users’ decision autonomy. To address these challenges, we explored the development of itinerary planning technologies through a human-centered approach. We aimed to balance guiding users in their decision-making with empowering them to plan tours independently. The result is CARES, an Artificial Intelligence-driven trip planner designed for autistic adults, which we present in this article. CARES applies a collaborative approach to developing itineraries, based on the exploitation of (i) AI technologies for information filtering and interactive itinerary planning that are robust to the data scarcity characterizing the autism domain; (ii) a user interface that reduces information overload and decision fatigue in information exploration. We tested CARES with 14 autistic adults, gathering insights to guide future design and improve the usability of Artificial Intelligence for neurodivergent users. The results indicate that our approach provides an accessible solution for enhancing the travel experiences of mid- to high-functioning autistic adults. In doing so, it contributes to more inclusive tourism. • We found that, despite difficulties, autistic adults wish to plan trips autonomously. • We propose a Human-Centered AI trip planner for mid/high-functioning ASD users. • Step-by-step guidance helps autistic users plan trips with limited effort. • The app empowers users to make choices while AI guides the process, ensuring balanced control. • The app balances user guidance and decision-making control.

User experience and trust in AI-assisted technologies are key factors in controlling their adoption. We investigate these aspects in an Agentic AI platform that integrates routine productivity services and exhibits different levels of autonomy: a manual baseline that lacks AI-driven automation, an Agentic AI with medium autonomy that requires user confirmation before acting, and an Agentic AI with high autonomy that acts proactively for low-stakes tasks. The study, involving 230 participants with heterogeneous professional backgrounds, examines how autonomy of the system affects user activity, user workload, perceived support, and trust. We found that both Agentic AI systems outperformed the baseline in user productivity. In task execution, they achieved a precision of over 82%, higher than the baseline’s 65%. The recall of the Agentic AI system with high autonomy was 63%. This denotes much higher throughput than the system without AI-driven automation (14%). The Agentic AI systems outperformed the baseline in workload reduction (NASA-TLX Aggregate score) with a statistically significant difference. Both AI-driven systems received equivalent or slightly higher trust than the baseline. However, the system with medium autonomy was the best at balancing productivity gains and user preferences for control. Specifically, the correlations between individual user characteristics (Desirability of Control and Propensity to Trust) and the resulting trust in the systems suggest that the influence of personal traits on system evaluation is least pronounced when automation is combined with explicit user intervention. These results encourage the adoption of user-controllable Agentic AI architectures in multitasking support.

Reproducibility lies at the basis of the empirical method: a novel approach will be widely adopted if its experimental results can be validated and reproduced by the community. Previous work on reproducibility in Information Retrieval (IR) has mainly addressed the reproducibility and replicability of offline experiments, with a few exceptions that replicate user studies. To the best of our knowledge, no previous work has investigated how reproducibility affects real users. In this paper, we do that by evaluating and comparing the reproducibility of an IR system both offline and online. We consider a reference system and generate a constellation of reproduced systems with varying parameters. We select 6 systems with different degrees of offline reproducibility. We then run a between-subjects online experiment with 280 participants and collect clicks to evaluate online reproducibility. Results show that real users do not perceive moderate variations of the reproducibility degree of systems, while they become relevant when the difference with the original system increases. Furthermore, we trained a click model to evaluate online reproducibility with simulated clicks. Results are not consistent with those from the user study, suggesting that better click models are needed to evaluate online reproducibility. Our data and source code are publicly available: https://github.com/angelogeninatti/reproducibilityLogs .

In the rapidly evolving landscape of technology and sustainability, leveraging Recommender Systems has emerged as a powerful tool for driving positive change. With a foundation in AI and data analytics, Recommender Systems can be effective in various domains, from e-commerce to energy management, inclusion and well-being. By harnessing the power of recommendation algorithms under a multi-stakeholder perspective, organizations and researchers can guide users towards more sustainable choices and behaviors, contributing to broader environmental and social goals. With this aim, our workshop provides a unique platform for researchers, practitioners, and platform owners to explore the integration of sustainability principles into Recommender Systems. Through presentations, discussions, and panels, participants can explore the theoretical foundations, practical implementations, and ethical and environmental considerations of sustainable Recommender Systems. By fostering collaboration and knowledge exchange, the workshop aims to catalyze innovation and inspire collective action towards a more sustainable future.

Autism Spectrum Disorder (ASD) affects sensory perception, making spatial exploration difficult. Recommender systems can assist ASD users by suggesting Points of Interest (POIs) aligned with their sensory preferences. However, demographic constraints, difficulties in engaging ASD users, and the complexity of obtaining sensory data position POI recommendation for ASD people as a low-resource problem. In this paper, we identify key challenges in developing such systems and present our ongoing efforts. Using a local ASD center as a use case, we are developing a structured user involvement protocol. From the limited data, we are deriving knowledge graphs (KGs) to model preferences and sensory aspects. We are then exploring KG-based techniques to generate paths from users to POIs to suggest. With psychologists, we are refining the paths structure to match varying complexity levels and translate them into natural language accessible for people with ASD.

The Workshop on Information Retrieval for Understudied Users (IR4U2) serves as a platform to highlight information retrieval (IR) research that directly impacts often understudied user groups. The second (IR4U2) workshop focuses on a user-centred AI perspective, which is vital for informing the design, development, and assessment of information retrieval systems that thoughtfully address the diverse needs of understudied populations, ensuring genuine accessibility and inclusivity. The objectives of IR4U2 are: (1) to build community and awareness by sharing AI and IR developments that serve underrepresented user groups in this research area; (2) to identify challenges and open issues along with lessons learned and challenges inherent to this area of research; and (3) to spark discussions that establish common frameworks for future research.

This special issue highlights state-of-the-art research in intelligent systems and technology for people with diverse abilities. To control scope, we pay particular attention to cognitive diversity, including but not limited to, neurodevelopmental disorders and autism, cognitive and learningdisabilities, and dementia. We introduce the papers in this special issue by contextualizing them according to different research areas. By curating leading-edge contributions in this area, we aim to raise awareness about research challenges and requirements inherent in the development and assessment of systems designed for these categories of users.

The current models for the explanation and justification of recommender systems results focus on qualitative and quantitative data about items, overlooking the power of images to describe the different aspects of experience that the consumer should expect from their selection to post-sales. In the present paper, we extend previous justification models by exploiting object recognition on images to support a service-oriented presentation of multimodal (textual, quantitative, and images) information about items. As a testbed for our model, we chose the home-booking domain. In a user study, we found that item comparison can be enhanced by empowering the user to filter multimodal data based on a set of evaluation dimensions describing the experience with items. These results encourage the introduction of service-based filters for multimodal information retrieval in product and service catalogs.

Abstract With the increasing demand for predictable and accountable Artificial Intelligence, the ability to explain or justify recommender systems results by specifying how items are suggested, or why they are relevant, has become a primary goal. However, current models do not explicitly represent the services and actors that the user might encounter during the overall interaction with an item, from its selection to its usage. Thus, they cannot assess their impact on the user’s experience. To address this issue, we propose a novel justification approach that uses service models to (i) extract experience data from reviews concerning all the stages of interaction with items, at different granularity levels, and (ii) organize the justification of recommendations around those stages. In a user study, we compared our approach with baselines reflecting the state of the art in the justification of recommender systems results. The participants evaluated the Perceived User Awareness Support provided by our service-based justification models higher than the one offered by the baselines. Moreover, our models received higher Interface Adequacy and Satisfaction evaluations by users having different levels of Curiosity or low Need for Cognition (NfC). Differently, high NfC participants preferred a direct inspection of item reviews. These findings encourage the adoption of service models to justify recommender systems results but suggest the investigation of personalization strategies to suit diverse interaction needs.

Recommender systems are designed to help users in situations of information overload. In recent years we observed increased interest in session-based recommendation scenarios, where the problem is to make item suggestions to users based only on interactions observed in an ongoing session, e.g., on an e-commerce site. However, in cases where interactions from previous user sessions are also available, the recommendations can be personalized according to the users’ long-term preferences, a process called session-aware recommendation. Today, research in this area is scattered, and many works only compare a newly proposed session-aware with existing session-based models. This makes it challenging to understand what represents the state-of-the-art. To close this research gap, we benchmarked recent session-aware algorithms against each other and against a number of session-based recommendation algorithms along with heuristic extensions thereof. Our comparison, to some surprise, revealed that (i) simple techniques based on nearest neighbors consistently outperform recent neural techniques and that (ii) session-aware models were mostly not better than approaches that do not use long-term preference information. Our work therefore points to potential methodological issues where new methods are compared to weak baselines, and it also indicates that there remains a huge potential for more sophisticated session-aware recommendation algorithms.

Abstract Recommender systems are tools that support online users by pointing them to potential items of interest in situations of information overload. In recent years, the class of session-based recommendation algorithms received more attention in the research literature. These algorithms base their recommendations solely on the observed interactions with the user in an ongoing session and do not require the existence of long-term preference profiles. Most recently, a number of deep learning-based (“neural”) approaches to session-based recommendations have been proposed. However, previous research indicates that today’s complex neural recommendation methods are not always better than comparably simple algorithms in terms of prediction accuracy. With this work, our goal is to shed light on the state of the art in the area of session-based recommendation and on the progress that is made with neural approaches. For this purpose, we compare twelve algorithmic approaches, among them six recent neural methods, under identical conditions on various datasets. We find that the progress in terms of prediction accuracy that is achieved with neural methods is still limited. In most cases, our experiments show that simple heuristic methods based on nearest-neighbors schemes are preferable over conceptually and computationally more complex methods. Observations from a user study furthermore indicate that recommendations based on heuristic methods were also well accepted by the study participants. To support future progress and reproducibility in this area, we publicly share the session-rec evaluation framework that was used in our research.

ACM PATCH 2020, organized in conjunction with the 28th International Conference on User Modeling, Adaptation and Personalization, is the latest event of the PATCH series, started in 2007 and held within the UMAP and IUI Conference series. We summarize the main ideas addressed in the papers accepted for publication in the workshop proceedings and for presentation at the event.

The suggestion of Points of Interest to people with Autism Spectrum Disorder (ASD) challenges recommender systems research because these users' perception of places is influenced by idiosyncratic sensory aversions which can mine their experience by causing stress and anxiety. Therefore, managing individual preferences is not enough to provide these people with suitable recommendations. In order to address this issue, we propose a Top-N recommendation model that combines the user's idiosyncratic aversions with her/his preferences in a personalized way to suggest the most compatible and likable Points of Interest for her/him. We are interested in finding a user-specific balance of compatibility and interest within a recommendation model that integrates heterogeneous evaluation criteria to appropriately take these aspects into account. We tested our model on both ASD and "neurotypical" people. The evaluation results show that, on both groups, our model outperforms in accuracy and ranking capability the recommender systems based on item compatibility, on user preferences, or which integrate these two aspects by means of a uniform evaluation model.

The benefits of neural approaches are undisputed in many application areas. However, today's research practice in applied machine learning---where researchers often use a variety of baselines, datasets, and evaluation procedures---can make it difficult to understand how much progress is actually achieved through novel technical approaches. In this work, we focus on the fast-developing area of session-based recommendation and aim to contribute to a better understanding of what represents the state-of-the-art.

Collaborative Filtering is largely applied to personalize item recommendation but its performance is affected by the sparsity of rating data. In order to address this issue, recent systems have been developed to improve recommendation by extracting latent factors from the rating matrices, or by exploiting trust relations established among users in social networks. In this work, we are interested in evaluating whether other sources of preference information than ratings and social ties can be used to improve recommendation performance. Specifically, we aim at testing whether the integration of frequently co-occurring interests in information search logs can improve recommendation performance in User-to-User Collaborative Filtering (U2UCF). For this purpose, we propose the Extended Category-based Collaborative Filtering (ECCF) recommender, which enriches category-based user profiles derived from the analysis of rating behavior with data categories that are frequently searched together by people in search sessions. We test our model using a big rating dataset and a log of a largely used search engine to extract the co-occurrence of interests. The experiments show that ECCF outperforms U2UCF and category-based collaborative recommendation in accuracy, MRR, diversity of recommendations and user coverage. Moreover, it outperforms the SVD++ Matrix Factorization algorithm in accuracy and diversity of recommendation lists.

Many collaborative recommender systems leverage social correlation theories to improve suggestion performance. However, they focus on explicit relations between users and they leave out other types of information that can contribute to determine users' global reputation; e.g., public recognition of reviewers' quality.

In Geographical Information search, map visualization can challenge the user because results can consist of a large set of heterogeneous items, increasing visual complexity. We propose a novel visualization model to address this issue. Our model represents results as markers, or as geometric objects, on 2D/3D layers, using stylized and highly colored shapes to enhance their visibility. Moreover, the model supports interactive information filtering in the map by enabling the user to focus on different data categories, using transparency sliders to tune the opacity, and thus the emphasis, of the corresponding data items. A test with users provided positive results concerning the efficacy of the model.

The presentation of search results in GIS can expose the user to cluttered geographical maps, challenging the identification of relevant information. In order to address this issue, we propose a visualization model supporting interactive information filtering on 2D/3D maps. Our model is based on the introduction of transparency sliders that enable the user to tune the opacity, and thus the emphasis, of data categories in the map. In this way, he or she can focus the maps on the most relevant types of information for the task to be performed. A test with users provided positive results concerning the efficacy of our model.

My PhD project focuses on the suggestion of information categories in exploratory search in a geographical domain. Geographical maps may challenge the user in the exploration of possibly complex information spaces, making difficult to find all the relevant data for the completion of her/his search task. I propose different models for concepts suggestion which, given a search query, allow the creation of clusters of categories useful for query expansion as a "you might be interested in" function. The training of these models is done by exploiting different types of information: search sessions, users» preferences and social data coming from Twitter.

Exploratory information search can challenge users in the formulation of efficacious search queries. Moreover, complex information spaces, such as those managed by Geographical Information Systems, can disorient people, making it difficult to find relevant data. In order to address these issues, we developed a session-based suggestion model that proposes concepts as a \em "you might also be interested in»» function, by taking the user»s previous queries into account. Our model can be applied to incrementally generate suggestions in interactive search. It can be used for query expansion, and in general to guide users in the exploration of possibly complex spaces of data categories. Our model is based on a concept co-occurrence graph that describes how frequently concepts are searched together in search sessions. Starting from an ontological domain representation, we generated the graph by analyzing the query log of a major search engine. Moreover, we identified clusters of ontology concepts which frequently co-occur in the sessions of the log via community detection on the graph. The evaluation of our model provided satisfactory accuracy results.

The Information Retrieval research has used semantics to provide accurate search results, but the analysis of conceptual abstraction has mainly focused on information integration. We consider session-based query expansion in Geographical Information Retrieval, and investigate the impact of semantic granularity (i.e., specificity of concepts representation) on the suggestion of relevant types of information to search for. We study how different levels of detail in knowledge representation influence the capability of guiding the user in the exploration of a complex information space. A comparative analysis of the performance of a query expansion model, using three spatial ontologies defined at different semantic granularity levels, reveals that a fine-grained representation enhances recall. However, precision depends on how closely the ontologies match the way people conceptualize and verbally describe the geographic space.

Textual queries are largely employed in information retrieval to let users specify search goals in a natural way. However, differences in user and system terminologies can challenge the identification of the user's information needs, and thus the generation of relevant results. We argue that the explicit management of ontological knowledge, and of the meaning of concepts (by integrating linguistic and encyclopaedic knowledge in the system ontology), can improve the analysis of search queries, because it enables a flexible identification of the topics the user is searching for, regardless of the adopted vocabulary. This paper proposes an information retrieval support model based on semantic concept identification. Starting from the recognition of the ontology concepts that the search query refers to, this model exploits the qualifiers specified in the query to select information items on the basis of possibly fine-grained features. Moreover, it supports query expansion and reformulation by suggesting the exploration of semantically similar concepts, as well as of concepts related to those referred in the query through thematic relations. A test on a data-set collected using the OnToMap Participatory GIS has shown that this approach provides accurate results.