Dipartimento di InformaticaUniversità degli Studi di Milano

Reliable and efficient machine learning

Reliability and AI systems

2024–20275 publications →theses available

This line of research focuses on the use of artificial intelligence methods to assess the reliability and security of systems. [Frasson and Malchiodi, 2024] extends support vector-based anomaly detection techniques to federated learning, [Biagiotti et al., 2025] investigates interpretable models for quench detection and localization in superconducting magnets, and [Paravisi et al., 2024] uses machine learning techniques to analyze the security of cryptographic algorithms. Particular attention is devoted to the reliability of AI-based systems: [Zanaboni et al., 2026] proposes a hypothesis testing procedure to detect covariate drift in queries submitted to a machine learning model, and [Malchiodi et al., 2027] detects hallucinations in large language models by applying anomaly detection techniques to the latent representations produced by the models themselves.

In collaboration with Prof.ssa Anna Maria Zanaboni, Prof. Marco Frasca, Prof. Massimo Walter Rivolta (Università degli Studi di Milano)

Compression of machine learning models

2021–20266 publications →theses available

Models learned from data, particularly deep neural networks, often have memory and transmission bandwidth requirements that exceed the resources available on embedded or resource-constrained devices. This line of research, initiated within the PRIN project Multicriteria Data Structures and Algorithms: from compressed to learned indexes, and beyond, investigates techniques for reducing the storage space required by a trained model while limiting the loss of accuracy. [Marinò et al., 2021b] introduced compact representations of deep neural networks based on Huffman coding, whose implementation is described in [Marinò et al., 2021a]. These representations are used in [Marinò et al., 2023a] to compress deep neural networks, while [Marinò et al., 2023b] presents an experimental comparison of compression techniques, providing recommendations for an informed choice among them. [Malchiodi et al., 2026] instead proposes regularizers that promote model compressibility directly during training. Compression techniques have been applied to estimating the Ki67 index in breast cancer on resource-constrained devices in [Gliozzo et al., 2024].

In collaboration with Prof. Marco Frasca (Università degli Studi di Milano)

Learned data structures

2022–20243 publications →theses available

Learned data structures extend classical ones by incorporating machine learning models trained on the data to be stored, with the aim of reducing storage space or query time. Within the PRIN project Multicriteria Data Structures and Algorithms: from compressed to learned indexes, and beyond, interaction between a classifier and the auxiliary components in learned Bloom filters has been investigated. [Fumagalli et al., 2022; Malchiodi et al., 2023] analyse how the choice of classifier affects storage space, false positive rate and query time, while [Malchiodi et al., 2024] relates these performance metrics to data complexity, providing recommendations for selecting and using these structures.

In collaboration with Prof. Marco Frasca (Università degli Studi di Milano), Prof. Raffaele Giancarlo (Università degli Studi di Palermo)

Fuzzy sets and learning from uncertain data

Data-driven induction of fuzzy sets

2013–20268 publications →theses available

A learning algorithm for fuzzy sets processing data labeled with their membership degrees has been proposed in [Malchiodi and Pedrycz, 2013; Malchiodi, 2019]. Such algorithm has been applied to axiom mining within semantic Web [Malchiodi and Tettamanzi, 2018] and to negative examples selection in bioinformatics [Frasca and Malchiodi, 2017; Frasca and Malchiodi, 2016]. This approach has been extended in [Cermenati et al., 2020] to the simultaneous induction of several fuzzy sets, and in [Malchiodi and Zanaboni, 2019] to shadowed sets. More recently, [Dashti Genave et al., 2026] studied techniques for compressing the membership functions learned in this way.

In collaboration with Prof.ssa Anna Maria Zanaboni, Prof. Marco Frasca (Università degli Studi di Milano), Prof. Witold Pedrycz (University of Alberta)

Earlier themes

Data quality-based learning2005–201310 publications →

In supervised learning, examples in the training sample are often assigned equal importance. This line of research investigates how to differentiate the contribution of each example through a numerical weight. This extension was formalised in [Malchiodi, 2008a] by introducing a general framework for relevance-based learning. The framework was applied to classification using support vector machines, deriving both linear [Apolloni and Malchiodi, 2006] and kernel-based [Apolloni et al., 2007d] algorithms. These algorithms were the subject of an initial theoretical analysis in [Apolloni et al., 2007e] and an experimental evaluation in [Malchiodi, 2009]. Applications of the framework to bioinformatics problems are described in [Malchiodi et al., 2010]. A similar approach was also adopted for regression in [Apolloni et al., 2010a; Malchiodi et al., 2009c; Apolloni et al., 2005c] and for learning from imbalanced data in [Malchiodi, 2013b].

Analysis of relations between granular computing and machine learning2005–20084 publications →

In the granular computing paradigm, information is represented and processed through granules, that is, groups of elements treated as units, allowing operations at different levels of abstraction. Its integration with machine learning is discussed in [Apolloni et al., 2008a]. Applications to regression have also been proposed, based on support vectors [Apolloni et al., 2008b; Apolloni et al., 2006e] and local search techniques [Apolloni et al., 2005c].

Machine learning for the life sciences

Knowledge graphs and LLM-based information extraction in biomedicine

2024–20264 publications →

Biomedical knowledge is scattered across numerous databases and a rapidly growing body of scientific literature. Knowledge graphs provide an effective means of integrating information from these heterogeneous sources, enabling it to be queried and analysed using machine learning techniques. [Cavalleri et al., 2024a; Cavalleri et al., 2024b] propose a system based on LLMs and graph machine learning to improve the quality of relations extracted from scientific articles on RNA-related topics. [Mesiti et al., 2026] describes a web application that supports experts in reviewing and validating biomedical knowledge graphs, while [Cavalleri et al., 2026] investigates the selection of negative examples for edge classification in these graphs.

In collaboration with Prof. Marco Mesiti (Università degli Studi di Milano)

Language models for protein and enzyme design

2023–20253 publications →

Protein sequences can be viewed as sentences written in a language whose alphabet consists of amino acids: large language models trained on corpora of sequences can be used to generate new protein sequences with desired functional properties. [Valentini et al., 2023] discusses the potential of LLMs for protein design and modelling. [Nicolini et al., 2024] shows that fine-tuning conditional Transformers on a specific protein family improves amino acid sequence prediction and enables the generation of new, biologically plausible sequences. [Nicolini et al., 2025] extends this approach to several enzyme categories, highlighting the benefits of fine-tuning for specific functional categories and evaluating the structural and functional properties of the generated sequences in silico.

In collaboration with Prof. Giorgio Valentini, Prof.ssa Elena Casiraghi, Prof. Marco Mesiti (Università degli Studi di Milano), Prof. Alberto Paccanaro (Fundação Getulio Vargas & Royal Holloway, University of London)

Negative sample selection in biological networks and knowledge graphs

2016–20266 publications →

In many supervised learning problems in bioinformatics, positive examples and unlabelled data are available: the latter may include both true negatives and positive cases that have not yet been identified. This line of research investigates how to select reliable negative examples from unlabelled data. In [Frasca and Malchiodi, 2017; Frasca and Malchiodi, 2016], the problem was addressed through a ranking based on fuzzy set membership functions, while [Frasca et al., 2017; Boldi et al., 2018] proposed a data representation designed to facilitate negative example selection for protein function prediction. In [Frasca et al., 2019], negative example selection was applied to gene prioritisation. More recently, [Cavalleri et al., 2026] compared strategies for selecting negative examples for edge classification in biomedical knowledge graphs. The paper received the Best Paper Runner-Up Award at the GLOW 2026 workshop.

In collaboration with Prof. Marco Frasca, Prof. Marco Mesiti (Università degli Studi di Milano)

Applications of machine learning

Machine learning in human and veterinary medicine, forensic sciences and cultural heritage

2021–20257 publications →theses available

This line of research investigates the application of machine learning and statistical analysis techniques to problems in veterinary medicine, forensic science and archaeology. In particular, [Galizzi et al., 2021; Bagardi et al., 2021] describe the use of statistical techniques to analyse the relationship between cardiovascular factors and mortality in dogs undergoing a specific treatment. [Casali et al., 2021] presents a pilot study on the use of classification algorithms to predict the type of vehicle involved in a pedestrian collision, while [Blandino et al., 2025] assesses the feasibility of estimating the height of a fatal fall using artificial intelligence techniques. In archaeology, [Zanaboni et al., 2022; Ruschioni et al., 2023] use classification algorithms to predict the provenance of pottery fragments from chemical element concentrations, while [Malchiodi et al., 2025] compares one-class and binary classifiers for the same task.

In collaboration with Prof.ssa Anna Maria Zanaboni, Prof.ssa Letizia Bonizzoni (Università degli Studi di Milano)

Earlier themes

ML-based COVID-19 risk prediction2020–20212 publications →

[Casiraghi et al., 2020; Esposito et al., 2021] describe the application of machine learning techniques to predicting COVID-19 severity in patients presenting to the emergency department.

In collaboration with Prof. Giorgio Valentini, Prof.ssa Elena Casiraghi, Prof. Marco Frasca (Università degli Studi di Milano)

Mining of knowledge bases in semantic Web2018–20203 publications →

Identifying potential axioms within sets of formulae is a computationally demanding problem. This line of research investigates how to address it by learning from formulae labelled with a quality score computed beforehand from a Semantic Web knowledge base. Approaches include fuzzy set learning algorithms [Malchiodi and Tettamanzi, 2018] and kernel-based regression techniques [Malchiodi et al., 2018]. [Malchiodi et al., 2020] analyses how the choice of learning algorithms and dimensionality reduction techniques applied to vector representations of axioms affects the results.

In collaboration with Prof. Célia Da Costa Pereira, Prof. Andrea Tettamanzi (Université de la Côte d'Azur)

Earlier research lines

Computing education and popularization

Teaching computer programming2009–202212 publications →

This line of research investigates computer science education, with a particular focus on programming. Contributions include an analysis of computer science teaching in Italian schools [Bellettini et al., 2014a] and a critique of the view that reduces programming to encoding algorithms in a programming language [Lonati et al., 2015]. Topics investigated include introductory programming through specific projects and tools [Bulgheroni and Malchiodi, 2009; Paterson et al., 2015], interdisciplinary learning activities connecting programming and music [Ludovico et al., 2017; Baratè et al., 2017a; Baratè et al., 2017b], and the teaching of advanced programming topics [Lonati et al., 2016; Lonati et al., 2017d]. A constructionist approach to programming education was analysed in [Monga et al., 2018; Lodi et al., 2019], while [Condorelli and Malchiodi, 2022] describes the design of a course on big data architectures in collaboration with an industry partner.

In collaboration with laboratorio ALaDDIn (Università degli Studi di Milano)

Popularization of informatics culture2012–202018 publications →

These activities, carried out with the ALaDDIn laboratory, aim to promote understanding of the foundations of computer science in schools and among a wider audience. They include computing competitions for students, such as Kangourou dell'Informatica [Lissoni et al., 2012; Lissoni et al., 2013; Lissoni et al., 2014; Lissoni et al., 2015] and the Italian edition of Bebras. The latter's tasks have been studied as teaching resources and analysed in terms of difficulty [Bellettini et al., 2015b; Lonati et al., 2017c; Calcagni et al., 2017; Lonati et al., 2017a; Morpurgo et al., 2018]. Constructionist activities have also been proposed to support the learning of programming and computational thinking, including activities based on music and LEGO® bricks [Baratè et al., 2017b; Baratè et al., 2017a; Monga et al., 2018; Lodi et al., 2019]. These initiatives are complemented by teacher training [Bellettini et al., 2015a; Bellettini et al., 2018a; Bellettini et al., 2018b] and contributions aimed at teachers and the general public [Monga et al., 2017; Bellettini et al., 2020].

In collaboration with laboratorio ALaDDIn (Università degli Studi di Milano)

Training of computing teachers2014–20209 publications →

[Bellettini et al., 2014c] introduces the algomotricity approach, which places automated information processing at the centre of computer science education. The aim is to move beyond teaching focused almost exclusively on how specific technological tools work [Lonati et al., 2015; Bellettini et al., 2014a; Bellettini et al., 2020]. The approach was evaluated in teacher qualification programmes [Bellettini et al., 2015a], with particular attention to the constructivist perspective [Bellettini et al., 2018b; Bellettini et al., 2018a]. The educational use of computing contests in non-competitive settings was also investigated [Lonati et al., 2017c], analysing how task presentation affects their educational effectiveness [Lonati et al., 2017a].

In collaboration with laboratorio ALaDDIn (Università degli Studi di Milano)

Computational thinking challenges2012–20189 publications →

This activity investigates the use of computing contests as learning resources in primary and secondary schools, emphasising their educational purpose over competition. It includes organising nationwide contests [Lissoni et al., 2012; Lissoni et al., 2013; Lissoni et al., 2014; Lissoni et al., 2015], critically analysing their outcomes [Bellettini et al., 2015b; Lonati et al., 2017a], and studying their use in teaching [Lonati et al., 2017c; Calcagni et al., 2017; Morpurgo et al., 2018].

In collaboration with laboratorio ALaDDIn (Università degli Studi di Milano)

Informal learning of computing2012–20179 publications →

The algomotricity approach introduced in [Bellettini et al., 2014c; Bellettini et al., 2014b] has been applied to teaching core computer science concepts, including information representation [Bellettini et al., 2012; Bellettini et al., 2013; Baratè et al., 2017a], programming fundamentals [Baratè et al., 2017b], and recursive and greedy algorithmic strategies [Lonati et al., 2016; Lonati et al., 2017d; Lonati et al., 2017b].

In collaboration with laboratorio ALaDDIn (Università degli Studi di Milano)

Statistical learning and algorithmic inference

Design of learning algorithms2013–20193 publications →

This line of research investigates algorithms for learning from partially labelled data or uncertain labels, alongside methods for fuzzy set induction. In particular, [Malchiodi and Legnani, 2014] proposes an extension of support vector classification algorithms that handles both partially labelled data and uncertain labels, while [Malchiodi and Pedrycz, 2013] introduces an algorithm for learning fuzzy set membership functions, subsequently adapted to shadowed set induction in [Malchiodi and Zanaboni, 2019].

Bootstrap techniques for regression algorithms2006–20095 publications →

Bootstrap techniques use data resampling to estimate the sampling distribution of a statistic and quantify the uncertainty of estimates. This line of research investigates a variant first proposed in [Apolloni et al., 2006a] and further developed in [Apolloni et al., 2009; Apolloni et al., 2007a], which enables the construction of confidence regions for regression curves without relying on the usual assumptions about the distribution of measurement errors. Applications to linear and nonlinear regression are described in [Apolloni et al., 2008c], while [Apolloni et al., 2007c] presents applications in medicine.

Development of inference models for machine learning problems2000–200715 publications →

This line of research develops Algorithmic Inference, a theoretical framework that unifies inferential problems in statistics, such as point and interval estimation of distribution parameters, and computer science, such as approximation error estimation in computational learning [Apolloni et al., 2006a; Apolloni et al., 2005e; Apolloni et al., 2002e; Apolloni et al., 2002d; Apolloni and Malchiodi, 2001b; Malchiodi, 2000]. The framework builds on earlier theoretical results on the sample complexity of learning problems [Apolloni and Malchiodi, 2001a]. It has been applied to estimating classification risk for support vector machines [Apolloni et al., 2007e; Apolloni et al., 2005b; Apolloni and Malchiodi, 2002; Apolloni and Malchiodi, 2001b] and constructing confidence regions for regression lines without assuming a Gaussian error distribution [Apolloni et al., 2005f; Apolloni et al., 2002f]. In medicine, it has been used to construct confidence regions for the hazard function associated with time to recurrence in specific cancers [Apolloni et al., 2007c; Apolloni et al., 2005g; Apolloni et al., 2002i].

Design of hardware-implementable statistics1996–20133 publications →

Dedicated hardware circuits for computing estimates from data can reduce processing times, but require algorithms compatible with architectural constraints. This line of research applied the inference among gossips model, developed in [Malchiodi, 1996], to the construction of a family of estimators for Bernoulli populations that can be implemented directly on pRAM boards [Apolloni et al., 1997]. The same model was subsequently applied to the study of information exchange in social networks [Apolloni et al., 2013].

Hybrid and neuro-symbolic systems

Automatic simplification of symbolic descriptions2002–20065 publications →

In computational learning theory, the structural risk minimisation principle balances model complexity against training error, with the aim of promoting generalisation. This line of research applies this principle to classifiers based on logical expressions in disjunctive or conjunctive normal form. In [Apolloni et al., 2006b; Apolloni et al., 2005h; Apolloni et al., 2003a; Apolloni et al., 2002h; Apolloni et al., 2002b], an algorithm was developed to simplify these expressions through stochastic optimisation of the parameters of the fuzzy sets that describe them.

Design of hybrid learning systems2000–200613 publications →

Hybrid learning systems combine subsymbolic modules, often based on neural networks, with symbolic modules based on logical constructs. This line of research investigates how to integrate these representations and other learning models. [Apolloni et al., 2005a; Apolloni et al., 2004a] describe a system that extracts independent Boolean components (bICA) from input data features. These components are interpreted as truth values and used to construct logical formulae that symbolically represent relationships among the data [Apolloni et al., 2006b; Apolloni et al., 2003a; Apolloni et al., 2002a; Apolloni et al., 2000]. The system was applied to emotion recognition from speech signals [Apolloni et al., 2004a]. Systems of this kind were also used to monitor driver attention through biosignals [Apolloni et al., 2004c; Apolloni et al., 2004b; Apolloni et al., 2003d; Apolloni et al., 2003c; Apolloni et al., 2003b], within the ORESTEIA project (mOdular hybRid artEfactS wiTh adaptivE functIonAlity, IST-2000-26091), funded by the European Union under the IST-FET area of the Fifth Framework Programme between 2001 and 2003. A second strand integrates a fuzzy system for measuring the relevance of training examples with classification and regression models. Specifically, [Apolloni and Malchiodi, 2006] describes integration with a linear support vector classifier, while [Apolloni et al., 2005c] presents integration with a linear regression model.

Automatic classification of emotions2000–20064 publications →

This work applied the Algorithmic Inference framework described in [Apolloni et al., 2006a; Malchiodi, 2000] to automatic emotion classification from audiovisual signals [Apolloni et al., 2004a; Apolloni et al., 2002a]. The research was conducted within the PHYSTA project (Principled Hybrid Systems: Theory and Applications), funded by the European Union under the TMR programme of the Fourth Framework Programme between 1998 and 2000. The results were presented at an international school on computational learning organised within the same project.

Intelligent systems for pervasive and ubiquitous computing2003–20046 publications →

The ORESTEIA project (mOdular hybRid artEfactS wiTh adaptivE functIonAlity) investigated the design, implementation and analysis of intelligent systems for pervasive and ubiquitous computing, which embed computing capabilities in the environment and everyday objects. The project was funded by the European Union under the IST-FET area of the Fifth Framework Programme between 2001 and 2003. As part of research into attention state detection [Kasderidis et al., 2003], a prototype was developed to recognise a car driver's attention state from physiological signals [Apolloni et al., 2004c; Apolloni et al., 2004b; Apolloni et al., 2003d; Apolloni et al., 2003c; Apolloni et al., 2003b].

Scientific computing and simulation

Applications of systems for scientific computation2006–201314 publications →

Scientific computing systems support simulations and the interactive, incremental exploration of mathematical problems, providing tools for designing educational activities [Bulgheroni and Malchiodi, 2009; Malchiodi, 2008b]. A commercial system was described in detail in [Malchiodi, 2007] and extended with functionality for information encoding [Malchiodi, 2006d], remote procedure calls [Malchiodi, 2006c; Malchiodi, 2006a], and the production of scientific documentation [Malchiodi, 2011]. Further extensions address optimisation [Malchiodi, 2006b], support vector learning [Malchiodi et al., 2009b; Malchiodi et al., 2009a], and software validation [Malchiodi, 2013a]. The resulting code underpins the simulations described in [Apolloni et al., 2007d; Apolloni and Malchiodi, 2006]. Finally, [Malchiodi, 2010] presents a machine learning library built on an open-source scientific computing system.

Study of population dynamics2002–20108 publications →

This line of research investigates the mathematical modelling of conflict situations through an alternative to classical game theory. In [Apolloni et al., 2006d; Apolloni et al., 2003e; Apolloni et al., 2002g; Apolloni et al., 2002c], two-player games are considered, modelling conflict through the approximation of the solution to an NP-hard problem. The Algorithmic Inference framework is used to determine how limited computational resources should be allocated to the players. [Apolloni et al., 2006c] extends the approach to team games. Biological applications are described in [Apolloni et al., 2007b; Apolloni et al., 2005d], while [Apolloni et al., 2010b] uses the model to determine the computation time to allocate to learning algorithms based on local error minimisation.