Abstract Android OS is today the most used Operating System for mobile devices. However, it is susceptible to several malware attacks that may seriously compromise the privacy and security of individuals and organizations. This paper proposes an approach based on a static analysis of decompiled Android PacKages (APKs) to extract critical APIs and detect Android malware. The main contributions lie in the adoption of a graph-based data engineering schema to represent APIs taken from the Function Call Graphs of decompiled APKs and the formulation of a graph-based deep learning approach for explainable malware detection. In particular, the proposed approach, named , implements a Graph Neural Network (GNN) for binary classification (malware versus goodware), and integrates algorithm to disclose how specific API classes and control-flow edges between API calls influence malware alerts. The proposed approach was evaluated by considering 26,527 Android APKs. The results of an extensive and in-depth evaluation show that the presented GNN model achieves higher accuracy than deep neural models trained with traditional API call sequence representations and publicly available related methods. On the other hand, it produces decision explanations that yield interesting insights into the malicious patterns of APKs and support root cause analysis of missed malware alarms.

This paper presents one of the first contributions in the context of Multimodal Predictive Process Monitoring (MM-PPM) . In recent years, Predictive Process Monitoring (PPM) has evolved at the intersection of process mining, machine learning, and data science, as organizations seek to anticipate the future course of ongoing processes. Traditional PPM mainly relies on structured event log data, but many real-world scenarios generate richer information, including text, images, audio, and video. MM-PPM promises to start addressing this rich data scenario by integrating complementary knowledge from heterogeneous modalities through modality-specific representations and information fusion techniques. The growing digitization of healthcare systems, combined with advances in Artificial Intelligence (AI), has accelerated AI-based PPM for analyzing sequences of clinical events, supporting decision-making, enabling personalized care, and improving clinical facility management. Given these characteristics, clinical pathways represent an ideal domain for experimenting with MM-PPM, as they may naturally involve diverse modalities such as structured records, free-text notes, or medical images. To handle multimodal information available with clinical pathways, we introduce MEDUSA , an MM-PPM approach for outcome prediction, which jointly processes medical image information coupled with the storytelling of structural records and text notes collected during the clinical pathway of a patient until the acquisition of the considered image. The evaluation of MEDUSA is done in a COVID-19 case study, to assess the performance of the proposed approach and explain how specific information within each modality influences the decisions of the predictive model.

Process discovery aims to automatically discover a process model to explain the behavior of event traces recorded in an event log during the execution of the activities of an underlying process. Several powerful process discovery algorithms are already formulated in process mining to identify regular control-flow structures in event logs and strike different trade-offs between the accuracy in capturing the behavior recorded in the event $\log$ and the complexity of the derived process model. This is commonly done under the assumption that log event traces are distributed according to the Pareto principle with a large portion of event traces held by a small fraction of top-frequent variants. However, the Pareto principle is not always satisfied in several real-life, complex processes. For example, the majority of log event traces produced in various healthcare or gaming processes is often spanned on a high number of top-frequent varianttraces. Various techniques (e.g. event filtering, trace extraction and trace abstraction) are already formulated in process mining to cope traditional process discovery algorithms also with event logs that do not conform the Pareto principle. Following this line of research, we explore the performance of a trace extraction method introduced to support the quest for Pareto-like event trace distribution during process discovery. The trace extraction is done resorting to a deep embedding representation of event traces, which sees traces at an abstraction level that removes noise and anomalous trace excerpt by enabling the discovery of simpler process models with higher accuracy. The deep embedding is used in combination with clustering. Experiments with several benchmark event logs show the effectiveness of the two proposed methods also compared to prior methods.

Open remote sensing science has been recently boosted by the free availability of Sentinel-2 images of planet Earth acquired with the Copernicus programme. In particular, processing open Sentinel-2 images with Artificial Intelligence (AI) techniques holds great potential for revolutionizing data science applications in many domains of Earth sciences. In this paper, we explore the potential of an unsupervised learning method designed to process Sentinel-2 images of Earth’s forest scenes and automate the inventory of forest tree dieback caused by bark beetle outbreaks. Specifically, we describe PHANTASM: a method to identify forest tree dieback patches performing the Change Vector Analysis (CVA) of bi-temporal Sentinel-2 images of forest scenes. While the traditional CVA strategy is based on the analysis of pixel-wise differences in spectral values, we enrich the Sentinel-2 spectrum with both a selection of Spectral Vegetation Indexes and a Spectral-Spatial Deep Embedding. The Spectral Vegetation Indexes are pre-defined combinations of spectral bands commonly designed to enhance the accuracy of semantic segmentation models trained to map bark beetle stress in spectral data. The Deep Embedding is a spectral-spatial representation of Sentinel-2 pixels trained with a deep neural network. In particular, we use a pre-trained, semantic segmentation U-Net to obtain the Deep Embedding that models the spatial relationship among neighbouring spectral pixels. We assess the effectiveness of the proposed method in a case study regarding bark beetle outbreaks in Sentinel-2 images of forest scenes in the Czech Republic.

Abstract Artificial Intelligence (AI) is transforming cybersecurity practices thanks to the amazing accuracy performance achieved with several AI-based malware detection systems. However, several recent studies have shown that AI decision models can be vulnerable to adversarial attacks. In malware detection scenarios, adversarial attacks are realistic manipulations of existing malware, which preserve the executable and malicious behaviour but evade the malware detection measures. In this study, we consider Windows Portable Executable (PE) malware, which is currently trending to prominent malware types, and we show that counterfactual explanations can be used to drive the generation of realistic adversarial Windows PE malware to evade AI-based detection. In particular, the proposed method OLIVANDER works in a black-box manner, which is the most restrictive attack option, as the evasion method interacts with the target decision system to evade by merely knowing the model input and output. The evaluation study explores the effectiveness of the proposed evasion method in terms of evasion ability, efficiency of computation, and attack transferability compared to two state-of-the-art evasion methods. In addition, the performed evaluation accounts for performances on commercial anti-malware systems.

An Emergency Department (ED) is a hospital facility that is staffed 24 hours a day, 7 days a week, and provides unscheduled services to patients whose health status requires immediate care. The management of the hospital admissions is one of the most critical processes for an ED. Several literature studies have recently used Artificial Intelligence (AI) methods to predict hospital admissions of ED patients. However, they generally handle ED journey features recording data with “one” multiplicity per journey. They often consider patients’ data collected at the end of ED journeys by rarely paying attention to obtain accurate decisions already during the early stages of ED journeys. Finally, they commonly use AI methods without equipping AI models with explanations of model decisions. Instead, this study illustrates an explainable Predictive Process Monitoring (PPM) method, called LEGOLAS , that uses a Large Language model (LLM) to obtain accurate and explainable decisions regarding the hospital admission of an ED patient. Decisions are already obtained in the early stages of an ED patient journey. A contribution of this study is the use of a story telling to describe ED patient journeys. This story telling accounts for the variety and multiplicity of information commonly recorded in free events logged for ED patients without requiring any complex preprocessing. Another contribution is the exploration of the accuracy performance of several foundation LLMs used with fine-tuning for the ED patient management process. A further contribution is an evaluation study with the real-life event log MIMICEL , to explore the impact and significance of the proposed method in terms of accuracy and earliness of decisions. This evaluation shows that LEGOLAS achieves overall accuracy equal to 0.76 by outperforming related AI methods that stop at an accuracy of 0.66. In addition, LEGOLAS achieves Fscore greater than 0.80 for the two majority classes of the study – Admitted and Home – after only twelve events observed in the ED patient journey. Finally, the evaluation explains which events and which categories of information better contribute to reveal the outcome of running ED patient journeys.

Abstract Forests play a key role in maintaining the balance of ecosystems, regulating climate, conserving biodiversity, and supporting various ecological processes. However, insect outbreaks, particularly bark beetle outbreaks, pose a significant threat to European spruce forest health by causing an increase in forest tree mortality. Therefore, developing accurate forest disturbance inventory strategies is crucial to quantifying and promptly mitigating outbreak diseases and boosting effective environmental management. In this paper, we propose a deep learning-based approach, named , that implements a CNN to detect tree dieback events in Sentinel-2 images of forest areas. To this aim, each pixel of a Sentinel-2 image is transformed into an imagery representation that sees the pixel within its surrounding pixel neighbourhood. We incorporate an attention mechanism into the CNN architecture to gain accuracy and achieve useful insights from the explanations of the spatial arrangement of model decisions. We assess the effectiveness of the proposed approach in two case studies regarding forest scenes in the Northeast of France and the Czech Republic, which were monitored using Sentinel-2 satellite in October 2018 and September 2020, respectively. Both case studies host bark beetle outbreaks in the considered periods.

Forecasting future states of running process instances is one of the main challenges of Predictive Process Monitoring (PPM). Several deep learning approaches have recently achieved a valuable accuracy performance by addressing this task. On the other hand, with the recent boom of Large Language Models (LLMs) in multiple fields, LLMs have started attracting attention in PPM research also. In this study, we leverage the rich context of textual data to transform information recorded in event logs in smart textual data ready for boosting accurate PPM learning. In detail, we propose LUPIN, a LLM approach to predict the activity suffix of a running process instance. First it encodes historical running process instances in semantic text stories formulated according to narrative templates that account for information recorded in the event log. Then it fine tunes a pre-trained LLM model – medium BERT – on the text stories of historic running instances of a business process, to predict the activity suffix of any future running instance of the same business process. Finally, LUPIN integrates the XAI Integrated Gradient (IG) algorithm to explain how each part of the textual description of a running process instance has an effect on the prediction of its activity completion. The experimental evaluation explores the accuracy performance of LUPIN compared to that of several related methods and draws insights from the explanation retrieved through the IG algorithm.

Forest tree dieback inventory plays a crucial role to improve forest management strategies. In this study, we explore the performance of a spectral-spatial machine learning approach used to analyse Sentinel-2 images to detect forest tree dieback events due to bark beetle infestation. We analyse the performance of classification models trained with Random Forest, XGBoost and Multi-Layer Perceptron, as well as semantic segmentation models trained with U-Net by accounting for both spectral and spatial information contained in the remote sensing data. We consider a set of Sentinel-2 images acquired in non-overlapping forest scenes from a region located in the Northeast of France. The selected scenes host bark beetle infestation hotspots originated from the mass reproduction of the bark beetle in the 2018 infestation. Results show that the U-Net model, trained accounting for spectral and spectral-spatial data, achieves the best performance. However, the simpler Random Forest model achieves competitive results with respect to the more complex one, namely U-Net.

Vision Transformers (ViTs) denote a family of attention-based deep learning techniques that have recently achieved amazing results in various problems related to the field of computer vision. In this paper, we explore the use of ViTs in problems of cyber-threat detection related to malware and network intrusion detection. In particular, we propose VINCENT, that is a novel deep neural method, which resorts to a color imagery representation of cyber-data by encoding related cyber-data features into neighboring color pixels. ViTs are trained from cyber-data images as teacher models, to extract explainable imagery signatures of cyber-data classes. This knowledge is extracted by leveraging the self-attention mechanism to give paired attention values between pairs of imagery patches. The signature knowledge, extracted through the ViT teacher, is, finally, used to train a smaller neural student model according to the knowledge distillation theory. Experiments with various benchmark cybersecurity datasets assess the accuracy of the student model VINCENT also compared to that of several state-of-the-art methods. In addition, it shows that VINCENT can obtain insights from explanations recovered through the self-attention mechanism of the ViT teacher.

Abstract Forest tree dieback inventory has a crucial role in improving forest management strategies. This inventory is traditionally performed by forests through laborious and time-consuming human assessment of individual trees. On the other hand, the large amount of Earth satellite data that are publicly available with the Copernicus program and can be processed through advanced deep learning techniques has recently been established as an alternative to field surveys for forest tree dieback tasks. However, to realize its full potential, deep learning requires a deep understanding of satellite data since the data collection and preparation steps are essential as the model development step. In this study, we explore the performance of a data-centric semantic segmentation approach to detect forest tree dieback events due to bark beetle infestation in satellite images. The proposed approach prepares a multisensor data set collected using both the SAR Sentinel-1 sensor and the optical Sentinel-2 sensor and uses this dataset to train a multisensor semantic segmentation model. The evaluation shows the effectiveness of the proposed approach in a real inventory case study that regards non-overlapping forest scenes from the Northeast of France acquired in October 2018. The selected scenes host bark beetle infestation hotspots of different sizes, which originate from the mass reproduction of the bark beetle in the 2018 infestation.

Abstract Ensemble learning is a strategy commonly used to fuse different base models by creating a model ensemble that is expected more accurate on unseen data than the base models. This study describes a new cyber-threat detection method, called , that uses ensemble learning coupled with adversarial training in deep learning, in order to gain accuracy with neural models trained in cybersecurity problems. The selection of the base models is one of the main challenges to handle, in order to train accurate ensembles. This study describes a model ensemble pruning approach based on eXplainable AI (XAI) to increase the ensemble diversity and gain accuracy in ensemble classification. We base on the idea that being able to identify base models that give relevance to different input feature sub-spaces may help in improving the accuracy of an ensemble trained to recognise different signatures of different cyber-attack patterns. To this purpose, we use a global XAI technique to measure the ensemble model diversity with respect to the effect of the input features on the accuracy of the base neural models combined in the ensemble. Experiments carried out on four benchmark cybersecurity datasets (three network intrusion detection datasets and one malware detection dataset) show the beneficial effects of the proposed combination of adversarial training, ensemble learning and XAI on the accuracy of multi-class classifications of cyber-data achieved by the neural model ensemble.

In this paper, we propose a novel predictive process monitoring approach, named JARVIS, that is designed to achieve a balance between accuracy and explainability in the task of next-activity prediction. To this aim, JARVIS represents different process executions (traces) as patches of an image and uses this patch-based representation within a multi-view learning scheme combined with Vision Transformers (ViTs). Using multi-view learning we guarantee good accuracy by leveraging the variety of information recorded in event logs as different patches of an image. The use of ViTs enables the integration of explainable elements directly into the framework of a predictive process model trained to forecast the next trace activity from the completed events in a running trace by utilizing self-attention modules that give paired attention values between two picture patches. Attention modules disclose explainable information concerning views of the business process and events of the trace that influenced the prediction. In addition, we explore the effect of ViT adversarial training to mitigate overfitting and improve the accuracy and robustness of predictive process monitoring. Experiments with various benchmark event logs prove the accuracy of JARVIS compared to several current state-of-the-art methods and draw insights from explanations recovered through the attention modules.

In this article, we introduce${\sf PROPHET}$, an innovative approach to predictive process monitoring based on Heterogeneous Graph Neural Networks.${\sf PROPHET}$is designed to strike a balance between accurate predictions and interpretability, particularly focusing on the next-activity prediction task. For this purpose, we represent the event traces recorded for different business process executions as heterogeneous graphs within a multi-view learning scheme combined with a heterogeneous graph learning approach. Using heterogeneous Graph Attention Networks (GATs), we achieve good accuracy by incorporating different characteristics of several events into graphs with different node types and leveraging different types of graph links to express relationships between event characteristics, as well as relationships between events. In addition, the use of a GAT model enables the integration of a modified version of the GNN Explainer algorithm to add the explainable component to the predictive model. In particular, the GNN Explainer algorithm is modified to disclose explainable information related to characteristics, events and relationships between events that mainly influenced the prediction. Experiments with various benchmark event logs prove the accuracy of${\sf PROPHET}$compared to several current state-of-the-art methods and draw insights from explanations recovered through the GNN Explainer algorithm.

This study describes a new cyber-threat detection method, named PANACEA, that uses Ensemble Deep Learning coupled with Adversarial Training and XAI, to gain accuracy with neural models trained in cybersecurity problems.

Abstract The Italian Public Administration (PA) relies on costly manual analyses to ensure the GDPR compliance of public documents and secure personal data. Despite recent advances in Artificial Intelligence (AI) have benefited many legal fields, the automation of workflows for data protection of public documents is still only marginally affected. The main aim of this work is to design a framework that can be effectively adopted to check whether PA documents written in Italian meet the GDPR requirements. The main outcome of our interdisciplinary research is INTREPID (art ficial i elligence for gdp complianc of ublic adm nistration ocuments), an AI-based framework that can help the Italian PA to ensure GDPR compliance of public documents. INTREPID is realized by tuning some linguistic resources for Italian language processing (i.e. SpaCy and Tint) to the GDPR intelligence. In addition, we set the foundations for a text classification methodology to recognise the public documents published by the Italian PA, which perform data breaches. We show the effectiveness of the framework over a text corpus of public documents that were published online by the Italian PA. We also perform an inter-annotator study and analyse the agreement of the annotation predictions of the proposed methodology with the annotations by domain experts. Finally, we evaluate the accuracy of the proposed text classification model in detecting breaches of security.

In this article we introduce${{\sf STARDUST}}$(event STream Analysis for pRocess Discovery Using Sampling sTragies), a process discovery approach that analyses a trace stream, in order to discover a process model that may change over time. The basic idea is to adopt a sampling technique to select the most representative trace variants to be considered for the process discovery, then to alert a concept drift as the trace variants to be sampled change over time and, finally, to trigger the discovery of a new process model as a drift is alerted. We formulate the proposed approach under the assumption that the trace distribution commonly follows the Pareto's principle (i.e., a few trace variants covers the majority of cases) which is commonly satisfied in several business processes. Experimental results on various benchmark event logs handled as streams show the effectiveness of the proposed approach also compared to a state-of-the- art concept drift detection approach.

[J1C2 Presentation Abstract at IEEE SERVICES 2022 for IEEE Transactions on Services Computing DOI 10.1109/TSC.2021.3051771]

Abstract Various applications in remote sensing demand automatic detection of changes in optical satellite images of the same scene acquired over time. This paper investigates how to leverage autoencoders in change vector analysis, in order to better delineate possible changes in a couple of co-registered, optical satellite images. Let us consider both a primary image and a secondary image acquired over time in the same scene. First an autoencoder artificial neural network is trained on the primary image. Then the reconstruction of both images is restored via the trained autoencoder so that the spectral angle distance can be computed pixelwise on the reconstructed data vectors. Finally, a threshold algorithm is used to automatically separate the foreground changed pixels from the unchanged background. The assessment of the proposed method is performed in three couples of benchmark hyperspectral images using different criteria, such as overall accuracy, missed alarms and false alarms. In addition, the method supplies promising results in the analysis of a couple of multispectral images of the burned area in the Majella National Park (Italy).

The predictive business process monitoring is a family of online approaches to predict the unfolding of running traces based on the knowledge learned from historical event logs. In this article, we address the task of predicting the next trace activity from the completed events in a running trace. This is an important business capability as counting on accurate predictions of the future activities may allow companies to guarantee the higher utilization by acting proactively in anticipation. We propose a novel predictive process approach that couples multi-view learning and deep learning, in order to gain predictive accuracy by accounting for the variety of information possibly recorded in event logs. Experiments with various benchmark event logs prove the effectiveness of the proposed approach compared to several recent state-of-the-art methods.

Predictive process monitoring (PPM) techniques have become a key element in both public and private organizations by enabling crucial operational support of their business processes. Thanks to the availability of large amounts of data, different solutions based on machine and deep learning have been proposed in the literature for the monitoring of process instances. These state-of-the-art approaches leverage accuracy as main objective of the predictive modeling, while they often neglect the interpretability of the model. Recent studies have addressed the problem of interpretability of predictive models leading to the emerging area of Explainable AI (XAI). In an attempt to bring XAI in PPM, in this paper we propose a fully interpretable model for outcome prediction. The proposed method is based on a set of fuzzy rules acquired from event data via the training of a neuro-fuzzy network. This solution provides a good trade-off between accuracy and interpretability of the predictive model. Experimental results on different benchmark event logs are encouraging and motivate the importance to develop explainable models for predictive process analytics.

Abstract Saliency detection mimics the natural visual attention mechanism that identifies an imagery region to be salient when it attracts visual attention more than the background. This image analysis task covers many important applications in several fields such as military science, ocean research, resources exploration, disaster and land-use monitoring tasks. Despite hundreds of models have been proposed for saliency detection in colour images, there is still a large room for improving saliency detection performances in hyperspectral imaging analysis. In the present study, an ensemble learning methodology for saliency detection in hyperspectral imagery datasets is presented. It enhances saliency assignments yielded through a robust colour-based technique with new saliency information extracted by taking advantage of the abundance of spectral information on multiple hyperspectral images. The experiments performed with the proposed methodology provide encouraging results, also compared to several competitors.

Predictive process monitoring has recently become one of the main enablers of data-driven insights in process mining. As an application of predictive analytics, process prediction is mainly concerned with predicting the evolution of running traces based on models extracted from historical event logs. This paper presents a process mining approach, which uses convolutional neural networks to equip the execution scenario of a business process with a means to predict the next activity in a running trace. The basic idea is to convert the temporal data enclosed in the historical event log of a business process into spatial data so as to treat them as images. To this purpose, every trace of the event log is first transformed into the set of its prefix traces (i.e. sequences of events that represent the prefix of a trace). These prefix traces are mapped into 2D image-like data structures. Created spatial data are finally used to train a Convolutional Neural Network, in order to learn a deep learning model capable to predict the next activity (i.e. the activity associated to the event occurring after the last event in the considered prefix trace). This predictive deep model can be employed as a powerful service to support participants in performing business processes since it guarantees a higher utilization by acting proactively in anticipation. Preliminary tests with two benchmark logs are carried out to investigate the viability of the proposed approach.

Managing geophysical data generated by emerging spatiotemporal data sources (e.g. geosensor networks) presents a growing challenge to Geographic Information System science. The presence of correlation poses difficulties with respect to traditional spatial data analysis. This paper describes a novel spatiotemporal analytical scheme that allows us to yield a characterization of correlation in geophysical data along the spatial and temporal dimensions. We resort to a multivariate statistical model, namely CoKriging, in order to derive accurate spatiotemporal interpolation models. These predict unknown data by utilizing not only their own geosensor values at the same time, but also information from near past data. We use a window-based computation methodology that leverages the power of temporal correlation in a spatial modeling phase. This is done by also fitting the computed interpolation model to data which may change over time. In an assessment, using various geophysical data sets, we show that the presented algorithm is often able to deal with both spatial and temporal correlations. This helps to gain accuracy during the interpolation phase, compared to spatial and spatiotemporal competitors. Specifically, we evaluate the efficacy of the interpolation phase by using established machine-learning metrics (i.e. root mean squared error, Akaike information criterion and computation time).

Process mining refers to the discovery, conformance, and enhancement of process models from event logs currently produced by several information systems (e.g. workflow management systems). By tightly coupling event logs and process models, process mining makes it possible to detect deviations, predict delays, support decision making, and recommend process redesigns. Event logs are data sets containing the executions (called traces) of a business process. Several process mining algorithms have been defined to mine event logs and deliver valuable models (e.g. Petri nets) of how logged processes are being executed. However, they often generate spaghetti-like process models, which can be hard to understand. This is caused by the inherent complexity of real-life processes, which tend to be less structured and more flexible than what the stakeholders typically expect. In particular, spaghetti-like process models are discovered when all possible behaviors are shown in a single model as a result of considering the set of traces in the event log all at once.To minimize this problem, trace clustering can be used as a preprocessing step. It splits up an event log into clusters of similar traces, so as to handle variability in the recorded behavior and facilitate process model discovery. In this paper, we investigate a multiple view aware approach to trace clustering, based on a co-training strategy. In an assessment, using benchmark event logs, we show that the presented algorithm is able to discover a clustering pattern of the log, such that related traces result appropriately clustered. We evaluate the significance of the formed clusters using established machine learning and process mining metrics.

This paper describes the principles and implementation of an algorithm for the classification of hyperspectral remote sensing images. The proposed approach is novel and can be included within the category of the spectral-spatial classification algorithms. The elements of novelty of the algorithm are as follows: (1) the implementation of two classifiers that work iteratively, each one exploiting the decision of the other to improve the training phase, and (2) the use of relational features based on the current labeling and on the spatial structure of the image. The two classifiers are fed with the spectral features and with the spatial features, respectively. The spatial features are built using the relative abundance of each class in a neighborhood of the pixel (homogeneity index), where the neighborhood is properly defined. An important contribution to the success of the method is the adoption of a multiclass classifier, the multinomial logistic regression, and a proper use of the posterior probabilities to infer the class labeling and build the relational data. The results of the two classifiers are eventually combined by means of an ensemble decision. The algorithm has been successfully tested on three standard hyperspectral images taken from the Airborne Visible-Infrared Imaging Spectrometer and ROSIS airborne sensors and compared with classification algorithms recently proposed in the literature.

Multi-Relational Data Mining (MRDM) refers to the process of discovering implicit, previously unknown and potentially useful information from data scattered in multiple tables of a relational database. Following the mainstream of MRDM research, we tackle the regression where the goal is to examine samples of past experience with known continuous answers (response) and generalize future cases through an inductive process. Mr-SMOTI, the solution we propose, resorts to the structural approach in order to recursively partition data stored into a tightly-coupled database and build a multi-relational model tree which captures the linear dependence between the response variable and one or more explanatory variables. The model tree is top-down induced by choosing, at each step, either to partition the training space or to introduce a regression variable in the linear models with the leaves. The tight-coupling with the database makes the knowledge on data structures (foreign keys) available free of charge to guide the search in the multi-relational pattern space. Experiments on artificial and real databases demonstrate that in general Mr-SMOTI outperforms both SMOTI and M5' which are two propositional model tree induction systems, and TILDE-RT which is a state-of-art structural model tree induction system.

In many real-time applications, such as wireless sensor network monitoring, traffic control or health monitoring systems, it is required to analyze continuous and unbounded geographically distributed streams of data (e.g. temperature or humidity measurements transmitted by sensors of weather stations). Storing and querying geo-referenced stream data poses specific challenges both in time (real-time processing) and in space (limited storage capacity). Summarization algorithms can be used to reduce the amount of data to be permanently stored into a data warehouse without losing information for further subsequent analysis. In this paper we present a framework in which data streams are seen as time-varying realizations of stochastic processes. Signal compression techniques, based on transformed domains, are applied and compared with a geometrical segmentation in terms of compression efficiency and accuracy in the subsequent reconstruction.

The automatic discovery of process models can help to gain insight into various perspectives (e.g., control flow or data perspective) of the process executions traced in an event log. Frequent patterns mining offers a means to build human understandable representations of these process models. This paper describes the application of a multi-relational method of frequent pattern discovery into process mining. Multi-relational data mining is demanded for the variety of activities and actors involved in the process executions traced in an event log which leads to a relational (or structural) representation of the process executions. Peculiarity of this work is in the integration of disjunctive forms into relational patterns discovered from event logs. The introduction of disjunctive forms enables relational patterns to express frequent variants of process models. The effectiveness of using relational patterns with disjunctions to describe process models with variants is assessed on real logs of process executions.

The amount of data produced by ubiquitous computing applications is quickly growing, due to the pervasive presence of small devices endowed with sensing, computing and communication capabilities. Heterogeneity and strong interdependence, which characterize ‘ubiquitous data’, require a (multi-)relat ional approach to their analysis. However, relational data mining algorithms do not scale well and very large data sets are hardly processable. In this paper we propose an extension of a relational algorithm for multi-level frequent pattern discovery, which resorts to data sampling and distributed computation in Grid environments, in order to overcome the computational limits of the original serial algorithm. The set of patterns discovered by the new algorithm approximates the set of exact solutions found by the serial algorithm. The quality of approximation depends on three parameters: the proportion of data in each sample, the minimum support thresholds and the number of samples in which a pattern has to be frequent in order to be considered globally frequent. Considering that the first two parameters are hardly controllable, we focus our investigation on the third one. Theoretically derived conclusions are also experimentally confirmed. Moreover, an additional application in the context of event log mining proves the viability of the proposed approach to relational frequent pattern mining from very large data sets.

In recent years, a growing interest has been given to trajectory data mining applications that permit to support mobility prediction with the aim of anticipating or pre-fetching possible services [3]. Proposed approaches typically consider only spatio-temporal information provided by collected trajectories. However, in some scenarios, such as that of tourist supporting, semantic information which express needs and interest of the user (tourist) should be taken into account. This semantic information can be extracted from textual documents already consulted by the tourists. In this paper, we present the application of the time-slice density estimation [1] that permits to suggest/predict the next destination of the tourist. In particular, time-slice density estimation permits to measure the rate of change of tourist’s interests at a given geographical position over a user-defined time horizon. Tourist interests depend both on the geographical position of the tourist with respect to a reference system and on semantic information provided by geo-referenced documents associated to the visited sites. Our basic assumption is that a tourist moves towards a close destination which is semantically consistent with her/his current profile as much as possible. Destinations that minimize the profile drift are suggested/predicted as next destinations.

We consider the problem of eliminating redundant Boolean features for a given data set, where a feature is redundant if it separates the classes less well than another feature or set of features. Lavrač et al. proposed the algorithm REDUCE that works by pairwise comparison of features, i.e., it eliminates a feature if it is redundant with respect to another feature. Their algorithm operates in an ILP setting and is restricted to two-class problems. In this paper we improve their method and extend it to multiple classes. Central to our approach is the notion of a neighbourhood of examples: a set of examples of the same class where the number of different features between examples is relatively small. Redundant features are eliminated by applying a revised version of the REDUCE method to each pair of neighbourhoods of different class. We analyse the performance of our method on a range of data sets.

Model trees are an extension of regression trees that associate leaves with multiple regression models. In this paper, a method for the data-driven construction of model trees is presented, namely, the Stepwise Model Tree Induction (SMOTI) method. Its main characteristic is the induction of trees with two types of nodes: regression nodes, which perform only straight-line regression, and splitting nodes, which partition the feature space. The multiple linear model associated with each leaf is then built stepwise by combining straight-line regressions reported along the path from the root to the leaf. In this way, internal regression nodes contribute to the definition of multiple models and have a "global" effect, while straight-line regressions at leaves have only "local" effects. Experimental results on artificially generated data sets show that SMOTI outperforms two model tree induction systems, M5' and RETIS, in accuracy. Results on benchmark data sets used for studies on both regression and model trees show that SMOTI performs better than RETIS in accuracy, while it is not possible to draw statistically significant conclusions on the comparison with M5'. Model trees induced by SMOTI are generally simple and easily interpretable and their analysis often reveals interesting patterns.