Stefania MONICA - personale UniMoRe

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Stefania MONICA

Professore Associato
Dipartimento di Scienze e Metodi dell'Ingegneria

Pubblicazioni

2023 - Delayed and Periodic Execution of Tasks in Jadescript Programming Language [Relazione in Atti di Convegno]
Petrosino, G.; Monica, S.; Bergenti, F.
abstract

Software agents are expected to timely act and to dynamically plan their activities, for example, to solve the complex collaboration problems of many real-world applications. The collaboration among agents requires the ability to reason about time to dynamically coordinate and to effectively adjust the frequency of periodic actions and reactions. For these and related reasons, an agent-oriented programming language is demanded to provide the programmer with effective means to schedule the execution of delayed and periodic tasks. This paper describes the new datatypes, and the related changes to some language constructs, that have been recently added to the Jadescript programming language to allow agents to effectively manage the dynamic scheduling of delayed and periodic tasks.

2023 - Special issue for the 36th Italian Conference on Computational Logic (CILC 2021) [Curatela]
Bergenti, F.; Monica, S.
abstract

2022 - A Comparative Study of Three Neural-Symbolic Approaches to Inductive Logic Programming [Relazione in Atti di Convegno]
Beretta, D.; Monica, S.; Bergenti, F.
abstract

An interesting feature that traditional approaches to inductive logic programming are missing is the ability to treat noisy and non-logical data. Neural-symbolic approaches to inductive logic programming have been recently proposed to combine the advantages of inductive logic programming, in terms of interpretability and generalization capability, with the characteristic capacity of deep learning to treat noisy and non-logical data. This paper concisely surveys and briefly compares three promising neural-symbolic approaches to inductive logic programming that have been proposed in the last five years. The considered approaches use Datalog dialects to represent background knowledge, and they are capable of producing reusable logical rules from noisy and non-logical data. Therefore, they provide an effective means to combine logical reasoning with state-of-the-art machine learning.

2022 - A Description of the Jadescript Type System [Relazione in Atti di Convegno]
Petrosino, G.; Iotti, E.; Monica, S.; Bergenti, F.
abstract

Jadescript is an agent-oriented programming language that benefits from JADE, the popular framework to develop multi-agent systems in Java. The major goal behind the introduction of Jadescript is to simplify the implementation of real-world multi-agent systems by devising a language with specific linguistic constructs for agent-oriented abstractions. However, Jadescript needs to be coherent and consistent across its several features to effectively achieve its goals. This paper discusses some of the most relevant decisions taken during the design of Jadescript by means of an informal description of its type system. The discussed type system includes ordinary types, as found in many other programming languages, but it also includes a few types that are needed to adequately support relevant agent-oriented abstractions.

2022 - Recent Neural-Symbolic Approaches to ILP Based on Templates [Relazione in Atti di Convegno]
Beretta, D.; Monica, S.; Bergenti, F.
abstract

Deep learning has been increasingly successful in the last few years, but its inherent limitations have recently become more evident, especially with respect to explainability and interpretability. Neural-symbolic approaches to inductive logic programming have been recently proposed to synergistically combine the advantages of inductive logic programming in terms of explainability and interpretability with the characteristic capability of deep learning to treat noisy, erroneous, and non-logical data. This paper surveys and briefly compares four relevant neural-symbolic approaches to inductive logic programming that have been proposed in the last five years and that use templates as an effective basis to learn logic programs from data.

2022 - Robust Software Agents with the Jadescript Programming Language [Relazione in Atti di Convegno]
Petrosino, G.; Monica, S.; Bergenti, F.
abstract

This paper discusses several recent additions to the Jadescript agent-oriented programming language that regard the effective detection and handling of exceptional and erroneous situations at runtime. These new features were introduced to better support the mission-critical level of robustness that software agents are normally demanded to exhibit. The description of these new features is supported by an analysis of the state of the art of exception handling in programming languages, and it is complemented by a discussion on planned future developments. First, the novel exception handling mechanism introduced in Jadescript is presented, and the conceptual similarities and differences with the exception handling mechanisms normally provided by mainstream programming languages are emphasized. Second, the recent additions to Jadescript designed to support failures in behaviours are described, and these additions are related to the novel exception handling mechanism. Finally, the recent language support to manage stale messages using dedicated message handlers is presented and discussed.

2022 - Toward a Kinetic Framework to Model the Collective Dynamics of Multi-agent Systems [Relazione in Atti di Convegno]
Monica, S.; Bergenti, F.; Zambonelli, F.
abstract

2021 - On the Design of an Artificial Player for a Popular Word Game [Relazione in Atti di Convegno]
Coffrini, A.; Monica, S.; Bergenti, F.
abstract

This paper describes the design of an implemented software system intended to accomplish a specific natural language processing task. The targeted task is a challenge of the Evaluation Campaign of Natural Language Processing and Speech Tools for Italian proposed in 2020. The challenge is to design and implement an artificial player for the closing game of a popular Italian television show. Given five words, the goal of the player is to find a word related to, but also different from, the given words. The design of the proposed artificial player is discussed by presenting the dataset used to acquire sufficient linguistic knowledge and by briefly describing the algorithm used to play the game. A preliminary experimental evaluation of the artificial player is also discussed.

2021 - Preliminary Experiments on an Improved Artificial Player for a Word Association Game [Relazione in Atti di Convegno]
Coffrini, A.; Monica, S.; Bergenti, F.
abstract

This paper presents recent developments of a software system that acts as an artificial player for a popular word association game. The game was proposed for the Evaluation Campaign of Natural Language Processing and Speech Tools for Italian in 2020, and it attracted the interest of various researchers. Several aspects of the recent developments of the artificial player are discussed, from the collection of the texts used to acquire sufficient linguistic knowledge, to the improvements of the algorithm employed to play the game. Preliminary, but encouraging, experimental results are also discussed in comparison with other artificial players for the same game.

2021 - Proceedings of the 36th Italian Conference on Computational Logic (CILC 2021) [Curatela]
Monica, S.; Bergenti, F.
abstract

2021 - Prototypes of productivity tools for the jadescript programming language [Relazione in Atti di Convegno]
Petrosino, G.; Iotti, E.; Monica, S.; Bergenti, F.
abstract

Jadescript is an agent-oriented programming language built on top of JADE. So far, the focus of the development of the language was on design choices, on syntax refinements, and on the introduction of expressions and constructs for agent-related abstractions and tasks. In this paper, a proposal to achieve the crucial goal of making Jadescript suitable for professional use is presented. The success of Jadescript, as a solid language to build real-world agent-based software systems, is necessarily related to its effective integration with mainstream development tools. In this paper, some of the productivity tools developed to integrate Jadescript with a mainstream development environment are presented as a way to promote the successful adoption of the language towards the community of JADE users.

2021 - Summary of a Citywide Meal Planning Service for Kids Based on Logic Programming [Relazione in Atti di Convegno]
de Felice, R.; Monica, S.; Bergenti, F.
abstract

This paper describes an implemented service, and associated mobile app, that has been used for the last five school years to support effective meal planning for kids in Parma, Italy. The service suggests a daily choice of one, two, or three dinner proposals based on what children are expected to eat at the canteens of nurseries, kindergartens, and primary schools. In addition, the service provides proposals for the lunches of non-school days to cover weekends and school holidays. Lunch and dinner proposals are generated by means of a dedicated meal planning service that uses logic programming to solve constraint satisfaction problems associated with meal planning problems. The adopted constraints ensure that the proposals for lunches and dinners are nutritionally balanced throughout the week and that seasonal proposals are preferred to promote the consumption of seasonal vegetables and fruits.

2021 - Two agent-oriented programming approaches checked against a coordination problem [Relazione in Atti di Convegno]
Iotti, E.; Petrosino, G.; Monica, S.; Bergenti, F.
abstract

This paper discusses two approaches to agent-oriented programming and compares them from a practical point of view. The first approach is exemplified by Jadescript, which is an agent-oriented programming language that has been recently proposed to simplify the adoption of JADE. The second approach is exemplified by Jason, which is currently one of the most popular agent-oriented programming languages. Jason can be configured to use JADE to support the distribution of agents, which ensures that the discussed comparison between the two approaches can also take into account the performance of implemented multi-agent systems. In order to devise a quantitative comparison, the two considered languages are used to solve the same coordination problem, and obtained implementations are compared to discuss advantages and drawbacks of the two approaches.

2021 - WETICE 2021 Preface [Curatela]
Yangui, S.; Monica, S.
abstract

2020 - An algorithm for accurate and robust indoor localization based on nonlinear programming [Articolo su rivista]
Monica, S.; Bergenti, F.
abstract

The study of techniques to estimate the position of mobile devices with a high level of accuracy and robustness is essential to provide advanced location based services in indoor environments. An algorithm to enable mobile devices to estimate their positions in known indoor environments is proposed in this paper under the assumption that fixed anchor nodes are available at known locations. The proposed algorithm is specifically designed to be executed on the mobile device whose position is under investigation, and it allows the device to estimate its position within the environment by actively measuring distance estimates from the anchor nodes. In order to reduce the impact of the errors caused by the arrangement of the anchor nodes in the environment, the proposed algorithm first transforms the localization problem into an optimization problem, and then, it solves the derived optimization problem using techniques inspired by nonlinear programming. Experimental results obtained using ultra-wide band signaling are presented to assess the performance of the algorithm and to compare it with reference alternatives. The presented experimental results confirm that the proposed algorithm provides an increased level of accuracy and robustness with respect to two reference alternatives, regardless of the position of the anchor nodes.

2020 - Exploratory experiments on programming autonomous robots in jadescript [Relazione in Atti di Convegno]
Iotti, E.; Petrosino, G.; Monica, S.; Bergenti, F.
abstract

This paper describes exploratory experiments to validate the possibility of programming autonomous robots using an agent-oriented programming language. Proper perception of the environment, by means of various types of sensors, and timely reaction to external events, by means of effective actuators, are essential to provide robots with a sufficient level of autonomy. The agent-oriented programming paradigm is relevant with this respect because it offers language-level abstractions to process events and to command actuators. A recent agent-oriented programming language called Jadescript is presented in this paper together with its new features specifically designed to handle events. Exploratory experiments on a simple case-study application are presented to show the validity of the proposed approach and to exemplify the use of the language to program autonomous robots.

2020 - Interval arithmetic to support effective indoor positioning of software agents [Articolo su rivista]
Monica, S.; Bergenti, F.
abstract

The provision of advanced location-based services in indoor environments is based on the possibility of estimating the positions of mobile devices with sufficient accuracy and robustness. An algorithm to allow a software agent hosted on a mobile device to estimate the position of its device in a known indoor environment is proposed under the ordinary assumption that fixed beacons are installed in the environment at known locations. Rather than making use of geometric considerations to estimate the position of the device, the proposed algorithm first transforms the localization problem into a related optimization problem, which is then solved by means of interval arithmetic to provide the agent with accurate and robust position estimates. The adopted approach solves a major problem that severely limits the accuracy of the position estimates that ordinary geometric algorithms provide when the beacons are positioned to maximize line-of-sight coverage. Experimental results confirm that the proposed algorithm provides position estimates that are independent of the positions of the beacons, and they show that the algorithm outperforms a well-known geometric algorithm.

2020 - Preface [Relazione in Atti di Convegno]
Yangui, S.; Monica, S.
abstract

2020 - Preliminary Experiments on the Use of Nonlinear Programming for Indoor Localization [Relazione in Atti di Convegno]
Monica, S.; Bergenti, F.
abstract

The research on methods to provide accurate and robust estimates of the positions of mobile devices in indoor scenarios is motivated by the urge to provide users with advanced location-based services. This paper presents preliminary experiments on an algorithm that enables software agents hosted on mobile devices to obtain estimates of their positions in known indoor environments if appropriate beacons are available at known locations. The experimented algorithm assumes that agents can use the sensors that devices provide to actively estimate their positions inside the environment by measuring the distances from the available beacons. In order to reduce the effects of the errors caused by the positions of the beacons, the discussed algorithm relies on the localization as optimization approach. In particular, the algorithm uses nonlinear programming to effectively solve the optimization problem that originates from the localization problem. Experimental results show that the discussed algorithm guarantees an improved level of robustness and accuracy with respect to a well-known and established alternative.

2020 - Special issue for the twentieth edition of the workshop 'From objects to agents' [Curatela]
Baldoni, M.; Bergenti, F.; Monica, S.; Vizzari, G.
abstract

2020 - The first twenty years of agent-based software development with JADE [Articolo su rivista]
Bergenti, Federico; Caire, Giovanni; Monica, Stefania; Poggi, Agostino
abstract

A recent survey provides convincing evidence that JADE is among the most widely used tools to develop agent-based software systems. It finds application in industrial settings and to support research, and it has been used to introduce students to software agents in various universities. This paper offers a perspective on the current state of JADE by first presenting a chronicle of the relevant events that contributed to make JADE what it is today. Then, this paper enumerates some of the abstractions that JADE helped to identify and that are now commonly adopted in the community of researchers and practitioners interested in software agents and agent-based software development. Such abstractions have been successfully applied to construct relevant software systems, and among them, this paper reports on a mission-critical system that uses the abstractions that JADE contributed to identify to serve millions of users every day. Finally, this paper discusses an outlook on the near future of JADE by sketching a recent project that could contribute to provide a new perspective on the use of JADE.

2019 - A bio-inspired approach to WiFi-based indoor localization [Relazione in Atti di Convegno]
Bergenti, F.; Monica, S.
abstract

In this paper, the problem of indoor localization is investigated using a bio-inspired approach. The proposed approach relies on the use of WiFi networks, which nowadays can be considered a commodity available in all indoor environments. WiFi signals are used to obtain estimates of the distance between a smart device, whose position needs to be estimated, and the fixed access points of the network, which are assumed to be in known positions. Once a given number of range estimates from each available access point has been acquired, proper range averages are performed to feed the proposed localization algorithm. According to the proposed approach, localization is formulated in terms of an optimization problem, which is solved using an algorithm inspired from particle swarm optimization. Such an algorithm has been integrated in an add-on module of JADE, which is intended to execute on the smart device whose position needs to be estimated, and which was tested in relevant indoor scenarios. Experimental results in tested scenarios are shown in the last part of the paper in order to evaluate the performance of the proposed bio-inspired localization algorithm.

2019 - A subdivision algorithm to reason on high-degree polynomial constraints over finite domains [Articolo su rivista]
Bergenti, F.; Monica, S.
abstract

This paper proposes an algorithm to reason on constraints expressed in terms of polynomials with integer coefficients whose variables take values from finite subsets of the integers. The proposed algorithm assumes that an initial approximation of the domains of variables is available in terms of a bounding box, and it recursively subdivides the box into disjoint boxes until a termination condition is met. The algorithm includes three termination conditions that allow using it for three related reasoning tasks: constraint satisfaction, enumeration of solutions, and hyper-arc consistency enforcement. Considered termination conditions are based on suitable lower and upper bounds for polynomial functions over boxes that are determined using new results proved in the paper. The algorithm is particularly appropriate to reason on high-degree polynomial constraints because the proposed method to determine lower and upper bounds can outperform alternative methods when high-degree polynomials in a moderate number of variables are considered.

2019 - Adaptive Computing (and Agents) for Enhanced Collaboration (ACEC 2019) [Relazione in Atti di Convegno]
Monica, S.; Bergenti, F.; Blake, M. B.; Cabri, G.; Wajid, U.
abstract

The 17th edition of the "Adaptive Computing (and Agents) for Enhanced Collaboration" (ACEC) track at WETICE 2019 focuses mostly on the area of adaptive agent-based techniques for the enterprise. The aim of the track is to bring together researches and practitioners from the fields of software agents and adaptive computing to present results and discuss innovative ideas. This report outlines the content of papers accepted for presentation at the track.

2019 - Experiments on robust indoor localization of mobile devices using interval arithmetic [Relazione in Atti di Convegno]
Monica, S.; Bergenti, F.
abstract

The lack of techniques and tools to estimate the position of mobile devices with high accuracy and robustness is one of the major causes that limit the provision of advanced location-based services in indoor environments. An algorithm to enable mobile devices to estimate their positions in known indoor environments is discussed in this paper under the assumption that fixed network nodes are available at known locations. The discussed algorithm is designed to allow devices to estimate their positions by actively measuring the distances from visible fixed nodes. In order to reduce the errors introduced by the arrangement of the fixed nodes in the environment, the discussed algorithm transforms the localization problem into an optimization problem, which is then solved using interval arithmetic. Experimental results on the use of the discussed algorithm with distance estimates obtained using ultra-wide band are presented to assess the performance of the algorithm and to compare it with a reference alternative. Presented experimental results confirm that the discussed algorithm provides an increased level of robustness with respect to the considered reference alternative with no loss of accuracy.

2019 - Hybrid indoor localization using WiFi and UWB technologies [Articolo su rivista]
Monica, Stefania; Bergenti, Federico
abstract

The interest in indoor localization has been increasing in the last few years because of the numerous important applications related to the pervasive diffusion of mobile smart devices that could benefit from localization. Various wireless technologies are in use to perform indoor localization, and, among them, WiFi and UWB technologies are appreciated when robust and accurate localization is required. The major advantage of WiFi technology is that it is ubiquitous, and therefore it can be used to support localization without the introduction of a specific infrastructure. The major drawback of WiFi technology is that it does not often ensure sufficient accuracy. On the contrary, indoor localization based on UWB technology guarantees higher accuracy with increased robustness, but it requires the use of UWB-enabled devices and the deployment of specific infrastructures made of UWB beacons. Experimental results on the synergic use of WiFi and UWB technologies for localization are presented in this paper to show that hybrid approaches can be used to effectively to increase the accuracy of WiFi-based localization. Actually, presented experimental results show that the use of a small number of UWB beacons together with an ordinary WiFi infrastructure is sufficient to significantly increase the accuracy of localization and to make WiFi-based localization adequate to implement relevant location-based services and applications.

2019 - Simple and effective sign consistency using interval arithmetic [Relazione in Atti di Convegno]
Bergenti, F.; Monica, S.
abstract

Polynomial constraints over finite domains are expressed as equalities, inequalities, and disequalities of polynomials with integer coefficients whose variables take values from finite subsets of the integers. They are an interesting type of constraints that can be used to model many combinatorial problems over the integers. Sign consistency is a type of local consistency proposed specifically to support reasoning on polynomial constraints over finite domains. Sign consistency is parameterized in terms of a bounding function that is used to extract relevant information from a constraint when its variables are restricted to take values from a finite box. Known results from the literature on interval arithmetic can be readily used to propose a simple bounding function to support sign consistency. Preliminary experimental results show that the proposed bounding function is a promising candidate to effectively reason on polynomial constraints over finite domains.

2018 - A kinetic model of the dynamics of compromise in large multi-agent systems [Relazione in Atti di Convegno]
Bergenti, F.; Monica, S.
abstract

Compromise is one of the primary phenomena that govern the dynamics of the opinion in multi-agent systems. In this paper, compromise is isolated from other phenomena, and it is studied using a statistical framework designed to investigate collective properties of large multi-agent systems. The proposed framework is completed with the details needed to model compromise, and differential problems which describe the dynamics of the opinion under suitable hypotheses are presented. Long-time asymptotic solutions of obtained differential problems are discussed to confirm that compromise makes multi-agent systems tend to reach consensus. It is proved that compromise makes all agents tend to share the same opinion, and that the value of the asymptotic opinion can be expressed in terms of the characteristics of the multi-agent system and of the initial distribution of the opinion. Obtained analytic results are confirmed by independent simulations in an illustrative case.

2018 - A probabilistic matrix factorization algorithm for approximation of sparse matrices in natural language processing [Articolo su rivista]
Tarantino, G.; Monica, S.; Bergenti, F.
abstract

This paper suggests a variation of a well-known probabilistic matrix factorization algorithm which is commonly used in data analysis and scientific computing, and which has been considered recently to serve natural language processing. The proposed variation is meant to take benefit from the fact that matrices processed in natural language processing tasks are normally sparse rectangular matrices with one dimension much larger than the other, and this can be used to ensure adequate accuracy with acceptable computation time. Preliminary experiments on real-world textual corpora show that the proposed algorithm achieves relevant improvements compared to the original one.

2018 - A Quantitative Assessment of the JADEL Programming Language [Relazione in Atti di Convegno]
Bergenti, Federico; Iotti, Eleonora; Monica, Stefania; Poggi, Agostino
abstract

This paper reports a quantitative assessment of JADEL, an agent-oriented programming language designed to implement JADE agents and multi-agent systems. The assessment is structured in two parts. The first part is intended to evaluate the effectiveness of JADEL for the concrete implementation of agent-based algorithms expressed using a pseudocode. The second part examines the functionality of the language regarding concurrency and message passing by comparing the implementation in JADEL of a set of benchmark algorithms with the corresponding implementations in Scala. The metrics introduced for the two parts of the assessment are meant to evaluate the expressiveness and ease of use of JADEL, and reported results are encouraging.

2018 - A scripting language for practical agent-oriented programming [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania; Petrosino, Giuseppe
abstract

This paper describes the features of a scripting language proposed to support the practical implementation of agents and multi-agent systems using an agent-oriented programming approach. Agents are programmed in terms of procedures to be executed when interesting events occur, and the language provides specific constructs to describe managed events and related procedures. Among possible events, those related to communication are supported by specific constructs because of their relevance for the implementation of multi-agent systems. The proposed language is characterised by a strongly expressive syntax largely inspired by modern scripting languages to promote readability and to make agent programs similar to pseudocodes. Such a feature ensures that the programmer can use the language to describe the reactions of agents to events at a high level of abstraction, with all the advantages that it brings in terms of software quality.

2018 - A Stochastic Model of Diffusion in Opinion Dynamics [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania
abstract

This paper studies analytically the dynamics of the opinion in multi-agent systems when only the sociological phenomenon known as diffusion is considered. First, the paper recalls a framework for the analytic study of opinion dynamics which has been already applied to describe the effects of a number of sociological phenomena. Then, the framework is specialized to the study of diffusion, according to which the opinion of an agent can be influenced by the social context. Diffusion is introduced in the framework by stating stochastic rules meant to describe at the microscopic level how diffusion contributes to change the opinion of an agent. The obtained model is used to derive collective and asymptotic properties of multi-agent systems when only diffusion is considered, which are verified against specific simulations shown in the last part of the paper. The paper is concluded with a recapitulation of presented results and an outline of future work.

2018 - Adaptive computing (and agents) for enhanced collaboration (ACEC 2018) [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico; Brian Blake, M.; Cabri, Giacomo; Wajid, Usman
abstract

The 16th edition of the »Adaptive Computing (and Agents) for Enhanced Collaboration» (ACEC) track at WETICE 2018 focuses mostly on the area of adaptive agent-based techniques for the enterprise. The objective of the track is to bring together researches from the fields of software agents and adaptive computing to present results and discuss in the context of adaptive techniques and enterprise collaboration. This report briefly reports on the content of accepted papers.

2018 - An experimental evaluation of agent-based indoor localization [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper discusses the possibility of accurately estimating the position of smart appliances in known indoor environments using agent technology. The proposed localization approach does not require specific infrastructures, nor it requires special on-board sensors, because it uses only WiFi signaling, which can be considered ubiquitous. Localization is performed using range estimates from fixed access points of the WiFi network with known positions. In order to derive the experimental results shown in the paper, a specific range-based localization algorithm, the Two-Stage Maximum-Likelihood localization algorithm, is considered. Results presented in the last part of the paper show that a proper processing on the WiFi-based range estimates allows obtaining position estimates which can be considered sufficiently accurate for many applications.

2018 - Constraint Logic Programming with Polynomial Constraints over Finite Domains [Articolo su rivista]
Bergenti, Federico; Monica, Stefania; Rossi, Gianfranco
abstract

This paper introduces an instantiation of the constraint logic programming scheme called CLP(PolyFD) in which variables take values from finite subsets of the integers and constraints are expressed as equalities, inequalities, and disequalities of polynomials with integer coefficients. Such constraints, which we call polynomial constraints over finite domains, can be treated effectively by means of a specific solver under the assumption that initial approximations of the domains of variables are available. The proposed solver deals with constraints in a canonical form and it uses the modified Bernstein form of polynomials to detect the satisfiability of constraints. The solver is complete and a preliminary assessment of its performance is reported.

2018 - Experimental results on agent-based indoor localization using WiFi signaling [Articolo su rivista]
Monica, S.; Bergenti, F.
abstract

This paper discusses experimental results on the possibility of accurately estimating the position of smart devices in known indoor environments using agent technology. Discussed localization approaches are based on WiFi signaling, which can be considered as an ubiquitous technology in the large majority of indoor environments. The use of WiFi signaling ensures that no specific infrastructures nor special on-board sensors are required to support localization. Localization is performed using range estimates from the fixed access points of the WiFi network, which are assumed to have known positions. The performance of two range-based localization algorithms are discussed. The first, called Two-Stage Maximum-Likelihood algorithm, is well-known in the literature, while the second is a recent optimization-based algorithm that uses particle swarm techniques. Results discussed in the last part of the paper show that a proper processing of WiFi-based range estimates allows obtaining accurate position estimates, especially if the optimization-based algorithm is used.

2018 - Group for localising a moving target in a warehouse with automated guided vehicles [Brevetto]
Monica, Stefania; Ferrari, Gianluigi; Magnani, M.; Oleari, Fabio; De Mola, F.
abstract

The present invention relates to a localization or position estimation group for a moving target, such as a person or a manual guided vehicle, in a warehouse or in an area to be monitored with at least one automatic guided vehicle, equipped with a unit for controlling the movement of the automatic guided vehicle itself, and at least one moving target .

2018 - Improving UWB-based localization in iot scenarios with statistical models of distance error [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

Interest in the Internet of Things (IoT) is rapidly increasing, as the number of connected devices is exponentially growing. One of the application scenarios envisaged for IoT technologies involves indoor localization and context awareness. In this paper, we focus on a localization approach that relies on a particular type of communication technology, namely Ultra Wide Band (UWB). UWB technology is an attractive choice for indoor localization, owing to its high accuracy. Since localization algorithms typically rely on estimated inter-node distances, the goal of this paper is to evaluate the improvement brought by a simple (linear) statistical model of the distance error. On the basis of an extensive experimental measurement campaign, we propose a general analytical framework, based on a Least Square (LS) method, to derive a novel statistical model for the range estimation error between a pair of UWB nodes. The proposed statistical model is then applied to improve the performance of a few illustrative localization algorithms in various realistic scenarios. The obtained experimental results show that the use of the proposed statistical model improves the accuracy of the considered localization algorithms with a reduction of the localization error up to 66%.

2018 - Kinetic models of relevant phenomena related to opinion dynamics [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper outlines recent analytic results regarding the dynamics of the opinion in large multi-agent systems. Discussed results are based on a unifying framework which takes inspiration from mathematical kinetic theories to describe analytically the long-time asymptotic properties of the opinion in large multi-agent systems. Different models to describe the effects of interactions among agents are considered to take into account different sociological phenomena that are known to govern the dynamics of the opinion. For each of such models, the proposed framework allows the analytic derivation of the dynamics of collective properties, such as the average opinion and its variance. Discussed results are in accordance with known empirical evidence, and their analytic form contributes to a solid theory of opinion dynamics.

2018 - Optimization-Based Robust Localization of JADE Agents in Indoor Environments [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper describes and evaluates a localization algorithm that was originally designed to overcome known issues of classic geometric localization algorithms, and that is now implemented in the localization add-on module of JADE. The algorithm is designed to support self-localization of agents running on smart devices in known indoor environments, and its current implementation acquires needed ranging information from ordinary WiFi infrastructures, with no need of dedicated infrastructures. First, the agent estimates the distances of the smart device where it is running from WiFi access points by using received signal strength during ordinary network discovery. Then, the agent uses computed distance estimates to generate estimates of its position by solving an appropriate optimization problem using particle swarm optimization. The robustness of the algorithm is discussed in the last part of the paper by comparing the performance of the algorithm against the performance of a classic algorithm in a representative scenario. Presented experimental results emphasize that the described algorithm is more robust than the classic alternative because it does not suffer from well-known numerical instability problems of geometric localization algorithms.

2017 - A Comparison between Asynchronous Backtracking Pseudocode and its JADEL Implementation [Relazione in Atti di Convegno]
Poggi, Agostino; Monica, Stefania; Iotti, Eleonora; Bergenti, Federico
abstract

In this paper, a comparison between the pseudocode of a well-known algorithm for solving distributed constraint satisfaction problems and the implementation of such an algorithm in JADEL is given. First, background and motivations behind JADEL development are illustrated. Then, we make a description of the problem and a brief introduction to JADEL. The core of this work consists in the translation of the algorithm pseudocode in JADEL code, which is described in details. Scope of the paper is to evaluate such a translation, in terms of closeness to pseudocode, complexity, amount of code written and performance.

2017 - A kinetic framework to study opinion dynamics in multi-agent systems [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania
abstract

In this paper we summarize an analytic framework to study opinion dynamics. Such a framework is inspired from physics and, in particular, from the kinetic theory of gases with different types of molecules, known as gas mixtures. By reinterpreting the molecules of gases as agents, and the collisions among molecules as interactions among agents, we show how to adapt the kinetic approach to the study of opinion dynamics in multi-agent systems. First, we briefly introduce the key ingredients of the kinetic theory of gas mixtures to clarify nomenclature and to emphasize the substantial differences with the proposed framework. Then, we show how the kinetic approach can be used to study opinion dynamics in multiagent systems, and how a variety of sociological phenomena can be accommodated in the proposed framework. In the last part of the paper we focus on two sociological phenomena, namely compromise and diffusion, and we describe analytic results concerning stationary profiles of the distribution of opinion, and of the temporal evolution of the average opinion and of the variance of the opinion.

2017 - Adaptive computing (and agents) for enhanced collaboration [Relazione in Atti di Convegno]
Bergenti, F.; Blake, M. B.; Cabri, G.; Jarrett, J.; Monica, S.; Wajid, U.
abstract

The 15th edition of the "Adaptive Computing (and Agents) for Enhanced Collaboration" track at WETICE 2017 focuses on the areas of adaptive agent-based services and adaptive techniques for enterprises. The purpose of the track is to bring together researches in the fields of software agents and adaptive computing as they relate to the context of adaptive techniques and enterprise collaboration. This report briefly discusses the content of the papers accepted for presentation in the track.

2017 - Agent-oriented model-driven development for JADE with the JADEL programming language [Articolo su rivista]
Bergenti, Federico; Iotti, Eleonora; Monica, Stefania; Poggi, Agostino
abstract

This paper describes, from motivations and main objectives to actual implementation, a novel agent-oriented programming language called JADEL. JADEL is designed to support the effective implementation of JADE agents and multi-agent systems in the scope of real-world model-driven development because it concretely helps developers by natively supporting agent-oriented abstractions, and because it is based on mature industrial-strength technologies. The four core abstractions that JADEL supports, namely agents, behaviours, communication ontologies, and interaction protocols, are presented by gradually introducing the specific syntaxes that the language provides for them. In the last part of the paper, a complete example of a simple JADEL multi-agent system is presented and discussed. Such an example is a well-known example from the official distribution of JADE and many programmers learned the basics of JADE from it. The choice of this example allows comparing JADEL source code with reference Java source code using JADE, and it clearly emphasizes the practical advantages of agent-oriented programming.Section 1 introduces and motivates the presented work. Section 2 surveys major AOP languages and, even if it cannot be considered exhaustive, it highlights the specific features of selected languages that have been relevant for the design of JADEL. Section 3 provides an overview of the features of JADE that are supported by JADEL. Section 4 presents the language in details by discussing main supported abstractions, and by specifying its formal syntax. Section 5 presents the most interesting parts of a complete example of the use of JADEL to develop a simple multi-agent system. Finally, Section 6 concludes the paper with a discussion of the current state of the presented work, and a preliminary assessment of the proposed language.

2017 - An analytic model of the impact of skeptical agents on the dynamics of compromise [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper studies analytically the dynamics of the opinion in multi-agent systems where two classes of agents coexist. The fact that the population of considered multi-agent systems is divided into two classes is meant to account for agents with different propensity to change their opinions. Skeptical agents, which are agents that are not inclined to change their opinions, can be modeled together with moderate agents, which are agents that are moderately open to take into account the opinions of the others. The studied analytic model of opinion dynamics involves only compromise, which describes how agents change their opinions to try to reach consensus. The adopted model of compromise is stochastic in order to give agents some level of autonomy in their decisions. Presented results show, analytically, that after a sufficient number of interactions consensus is reached, regardless of the initial distribution of the opinion. Analytic results are confirmed by simulations shown in the last part of the paper.

2017 - An Analytic Study of Opinion Dynamics in Multi-Agent Systems [Articolo su rivista]
Monica, Stefania; Bergenti, Federico
abstract

This paper presents an analytic approach that can be used to study opinion dynamics in multi-agent systems. The results of such an analytic approach can be used as a descriptive tool capable of predicting the long-term properties of a multi agent system, and they can also be considered a prescriptive tool that supports the design of multi-agent systems with desired asymptotic characteristics. The agents that form the multi-agent system are divided into disjoint classes characterized by different values of fixed parameters to account for the specific behaviors of single agents. Each class is characterized by the number of agents in it, by the initial distribution of the opinion, and by the characteristic propensity of single agents to change their respective opinions when interacting with other agents. The proposed approach is based on the possibility of interpreting the dynamics of the opinion in terms of the kinetic theory of gas mixtures, which allows expressing the dynamics of the average opinion of each class in terms of a suitable differential problem that can be used to derive interesting asymptotic properties. Analytic solutions of the obtained differential problem are derived and it is shown that, under suitable hypotheses, the average opinions of all classes of agents converge to the same value. The results presented in this paper differ from those commonly derived in standard kinetic theory of gas mixtures because the microscopic equations which describe the effects of interactions among agents are explicitly meant to model opinion dynamics, and they are different from those normally used to describe collisions among molecules in a gas. All presented analytic results are confirmed by simulations presented at the end of the paper.

2017 - An optimization-based algorithm for indoor localization of JADE agents [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper describes and evaluates an optimizationbased localization algorithm which has been recently implemented to enrich the possibilities of the localization add-on module for JADE. The described algorithm targets indoor scenarios and it enables localization of JADE agents running on smart devices in known environments, provided that a conventional WiFi network is present. The algorithm assumes that WiFi access points in fixed and known positions are available, and it estimates the position of the smart device where the agent is running using estimates of the distance between the smart device and each access point. Distance estimates are used to build an optimization problem, whose solution is an estimate of the position of the smart device. The described algorithm uses particle swarm optimization to solve the built optimization problem, but it is open to the adoption of other optimization techniques. The validity of the proposed approach is supported by experimental results shown in the last part of the paper.

2017 - An overview of kinetic approaches to study consensus formation [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper discusses some recent results in the study of opinion dynamics and consensus formation in multi-agent systems. While results in these fields are typically obtained by simulation, the adoption of the approach inspired by kinetic theory of gases allows deriving analytic results. More precisely, analytic relationships between the parameters of the model and the asymptotic characteristics of the systems can be analytically determined. Various models inspired from kinetic theory of gases have been studied. For instance, different microscopic phenomena can be investigated, such as compromise and diffusions, and both deterministic and stochastic parameters have been used to model such phenomena. Recently, models inspired from kinetic theory of gas mixtures have also been introduced in the context of opinion dynamics. Such models allow studying multi-agent systems in which different classes of agents coexist. Agents belonging to different classes may be associated with different features, such as the initial distribution of the opinion and the propensity of agents to change their opinions when interacting with other agents. A discussion on the features of different models is presented in this paper.

2017 - Experimental evaluation of agent-based localization of smart appliances [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper presents an experimental evaluation of the performance of a novel add-on module for JADE intended to provide agents with estimates of their positions in known indoor environments with no need of dedicated infrastructures or specific onboard devices. First, the paper motivates the work and it details relevant assumptions regarding the applicability of the proposed module. The framework that the module provides to host localization algorithms is outlined, and the specific nomenclature is introduced. Then, the algorithm which ships with the module is briefly presented. Finally, the experimental campaign used to assess the performance of localization is detailed. Experimental results show that the accuracy of stationary localization is sufficient for envisaged application scenarios.

2017 - Hyper-arc consistency of polynomial constraints over finite domains using the modified Bernstein form [Articolo su rivista]
Bergenti, Federico; Monica, Stefania
abstract

This paper describes an algorithm to enforce hyper-arc consistency of polynomial constraints defined over finite domains. First, the paper describes the language of so called polynomial constraints over finite domains, and it introduces a canonical form for such constraints. Then, the canonical form is used to transform the problem of testing the satisfiability of a constraint in a box into the problem of studying the sign of a related polynomial function in the same box, a problem which is effectively solved by using the modified Bernstein form of polynomials. The modified Bernstein form of polynomials is briefly discussed, and the proposed hyper-arc consistency algorithm is finally detailed. The proposed algorithm is a subdivision procedure which, starting from an initial approximation of the domains of variables, removes values from domains to enforce hyper-arc consistency.

2017 - Indoor localization of JADE agents without a dedicated infrastructure [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper describes and compares two of the algorithms for indoor localization that are implemented in the localization add-on module for JADE. Described algorithms perform localization of agents running on smart devices in known indoor environments using only received WiFi signals from access points. First, distance estimates from access points are computed using received signal strength in routinary network discovery. Then, computed distance estimates are used to generate estimates of the position of the smart device that hosts the agent using one of described algorithms. The first algorithm, known as two-stage maximum-likelihood algorithm, is a well-known technique and it is considered a point of reference to evaluate the performance of other algorithms. The second algorithm, which has been recently introduced to overcome numerical-instability problems of classic geometric algorithms, works by turning localization into an optimization problem which is effectively solved using particle swarm optimization. In order to show the applicability of the proposed algorithms, the last part of the paper shows experimental results obtained in an illustrative indoor scenario, which is representative of envisioned applications.

2017 - Opinion dynamics in multi-agent systems: selected analytic models and verifying simulations [Articolo su rivista]
Monica, Stefania; Bergenti, Federico
abstract

In this paper opinion dynamics in multi-agent systems is investigated analytically using a kinetic approach. Interactions among agents are interpreted as collisions among molecules in gases and opinion dynamics is described according to the Boltzmann equation. Starting from a microscopic description of single interactions, global properties of the opinion distribution are derived analytically. The proposed analytic model is general enough to allow reproducing features of real societies of agents, such as positive and negative influences and bounded confidence, which are typically used to study opinion distribution models. Analytic results relative to emergent and global characteristics of considered multi-agent systems are verified by simulations obtained via direct implementation of the proposed microscopic interactions rules. Simulations confirm analytic results.

2017 - Outline of a generalization of kinetic theory to study opinion dynamics [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper presents an analytic framework to study the dynamics of the opinion in multi-agent systems. In the proposed framework, each agent is associated with an attribute which represents its opinion, and the opinion of an agent changes because of interactions with other agents, without supervised coordination. Each interaction involves only two agents, and it corresponds to an exchange of messages. The framework assumes that time is modeled as a sequence of discrete steps, which do not necessarily have the same duration, and that at each step two random agents interact. Various sociological phenomena can be incorporated in the proposed framework, and the framework allows studying macroscopic properties of a system starting from microscopic models of such phenomena, obtaining analytic results. In detail, the proposed framework is inspired by the kinetic theory of gas mixtures, which relies on the use of balance equations that can be properly adopted to study opinion dynamics in a multi-agent system. After a short introduction on the kinetic theory of gas mixtures, this paper shows how the main ideas behind it can be generalized to study the dynamics of the opinion in multi-agent systems starting from a detailed description of microscopic interactions among agents.

2017 - Overview of a formal semantics for the JADEL programming language [Relazione in Atti di Convegno]
Bergenti, Federico; Iotti, Eleonora; Monica, Stefania; Poggi, Agostino
abstract

This paper outlines a first proposal of a formal semantics for the JADEL programming language. JADEL is an agent-oriented programming language based on JADE that has been recently proposed to ease the adoption of JADE, and to promote its use. In previous works, JADEL was specified at the syntax level, and only an informal semantics was given. The major contribution of this paper is to outline a formalization of the semantics of JADEL to complement previous works and to allow reasoning on JADEL agents and multi-agent systems. First, the paper provides a brief recall on JADEL by describing its main abstractions and their specific syntactic constructs. Then, a discussion of the proposed operational semantics based on transition systems is described. Finally, a detailed operational semantics of only some relevant constructs is given. The validity of the proposed approach is discussed in the conclusion of the paper, together with directions of future developments.

2017 - Satisfaction of polynomial constraints over finite domains using function values [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania
abstract

This paper shows how the solutions of constraint satisfac-tion problems that involve only polynomial constraints over finite do-mains can be enumerated by computing the values of related polynomial functions at appropriate points. The proposed algorithm first transforms constraints, which are expressed as equalities, inequalities, and disequal-ities of polynomials with integer coefficients and integer variables, into a canonical form that uses only inequalities. Then, starting from a bound-ing box, which is supposed to be known, the algorithm recursively sub-divides the box into disjoint boxes and it records boxes whose elements satisfy all constraints. The subdivision is driven by the study of the sign of polynomial functions over boxes, which is performed by means of a method that uses only the coefficients of polynomials and the values of functions at the corners of boxes.

2017 - Two analytic models of compromise in multi-agent systems [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper studies compromise, which is the tendency of agents to move their opinions towards those of agents they interact with, trying to reach consensus. Compromise is one of the most important phenomena in the study of opinion dynamics, and this paper presents two analytic models to study it. First, agents are considered deterministic and a preliminary model of the effects of compromise is derived. Then, the model is generalized to give agents some level of autonomy by modelling their behaviour in terms of a stochastic process. Both models are analytic and they can be used to study collective properties of multi-agent systems starting from the details of single interactions among agents. Analytic results concerning the conservation of the average opinion for both models are verified by simulation in the last part of the paper.

2016 - A case study of the JADEL programming language [Relazione in Atti di Convegno]
Bergenti, Federico; Iotti, Eleonora; Monica, Stefania; Poggi, Agostino
abstract

This paper presents and discusses a first complete example of the use of JADEL. JADEL is a novel agent-oriented domain-specific programming language built on top of JADE, the well-known agent platform which provides solid agent technology and several tools for the creation of agents and multi-agent systems. The purpose of JADEL is to make the development of JADE agents and multi-agent systems easier and clearer by means of specific abstractions and a lighter syntax. In order to understand, and properly assess, the actual advantages of using JADEL, a well-known JADE demo that uses JADEspecific features like ontologies and interaction protocols has been rewritten in JADEL. This paper first briefly presents the main features of JADEL, then it discusses the rewritten demo and compares it with original JADE code.

2016 - A comparison of accurate indoor localization of static targets via WiFi and UWB ranging [Capitolo/Saggio]
Monica, Stefania; Bergenti, Federico
abstract

This paper compares Ultra-Wide Band (UWB) and WiFi technologies as sources of information for accurate localization of static targets in indoor scenarios. Such technologies offer different localization accuracy and they are also characterized by different applicability. UWB provides very accurate localization information, but it requires a dedicated infrastructure and it is not yet widely available in mobile appliances. WiFi gives less accurate localization information but it is integrated in all modern mobile appliances and it does not require a dedicated infrastructure. This paper details on accuracy versus wide applicability trade-off and it provides quantitative criteria to choose one technology or the other. The discussed results are obtained using a new add-on module for JADE which allows embedding diverse sources of ranging information and localization algorithms.

2016 - A group for localising a moving target in a warehouse with automated guided vehicles [Working paper]
Monica, S.; Ferrari, G.; Magnani, M.; Oleari, F.; De Mola, F.
abstract

2016 - A study of consensus formation using kinetic theory [Capitolo/Saggio]
Monica, Stefania; Bergenti, Federico
abstract

In this paper consensus formation in multi-agent systems is studied using the framework of kinetic theory of gases. This can be done by interpreting agents as the molecules of a gas and interactions among agents as the collisions among the molecules. Each agent can interact with any other agent in the considered system and interactions are binary, i.e., they involve only two agents at a time. Under such hypothesis, starting from a microscopic model which describes the effects of interactions in a pair of agents, we derive, analytically, global properties of the system, such as the conservation of the average opinion. Simulation results show that the proposed kinetic approach allows reaching consensus and the velocity of convergence to consensus depends, as expected, on the parameters of the model.

2016 - A subdivision approach to the solution of polynomial constraints over finite domains using the modified Bernstein form [Capitolo/Saggio]
Bergenti, Federico; Monica, Stefania; Rossi, Gianfranco
abstract

This paper discusses an algorithm to solve polynomial constraints over finite domains, namely constraints which are expressed in terms of equalities, inequalities and disequalities of polynomials with integer coefficients whose variables are associated with finite domains. The proposed algorithm starts with a preliminary step intended to rewrite all constraints to a canonical form. Then, the modified Bernstein form of obtained polynomials is used to recursively restrict the domains of variables, which are assumed to be initially approximated by a bounding box. The proposed algorithm proceeds by subdivisions, and it ensures that each variable is eventually associated with the inclusion maximal finite domain in which the set of constraints is satisfiable. If arbitrary precision integer arithmetic is available, no approximation is introduced in the solving process because the coefficients of the modified Bernstein form are integer numbers.

2016 - A swarm-based approach to real-time 3D indoor localization: Experimental performance analysis [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

In this paper, the problem of indoor localization in wireless networks is addressed relying on a swarm-based approach. We assume to know the positions of a few number of sensor nodes, denoted as anchor nodes (ANs), and we aim at finding the position of a target node (TN) on the basis of the estimated distances between each AN and the considered TN. Since ultra wide band (UWB) technology is particularly suited for localization purposes (owing to its remarkable time resolution), we consider a network composed of UWB devices. More precisely, we carry out an experimental investigation using the PulsOn 410 ranging and communication modules (RCMs) produced by time domain. Using four of them as ANs and one of them as TN, various topologies are considered in order to evaluate the accuracy of the proposed swarm-based localization approach, which relies on the pairwise (AN-TN) distances estimated by the RCMs. Then, we investigate how the accuracy of the proposed localization algorithm changes if we apply to the distance estimates a recently proposed stochastic correction, which is designed to reduce the distance estimation error. Our experimental results show that a good accuracy is obtained in all the considered scenarios, especially when applying the proposed swarm-based localization algorithm to the stochastically corrected distances. The obtained results are satisfying also in terms of software execution time, making the proposed approach applicable to real-time dynamic localization problems.

2016 - An analytic study of opinion dynamics in multi-agent systems with additive random noise [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

In this paper we analytically derive macroscopic properties of the temporal evolution of opinion distribution in multi-agent systems under the influence of additive random noise. Proper rules which describe how the opinion of agents are updated after their interactions are given. Such rules involve a deterministic part, related to compromise, and a stochastic part, in terms of an additive random noise. Starting from the microscopic interaction rules among agents, macroscopic properties of the system are derived using an approach based on kinetic theory of gases. In particular, the stationary profiles of opinion distribution are derived analytically. In the last part of the paper, some illustrative examples of stationary profiles are presented.

2016 - Analytic study of opinion dynamics in multi-agent systems with two classes of agents [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper describes a model for opinion dynamics in multi-agent systems composed of two classes of agents. Each class is characterized by distinctive values of the parameters that govern opinion dynamics. The proposed model is inspired by kinetic theory of gases, according to which macroscopic properties of gases are described starting from microscopic interactions among molecules. By interpreting agents as molecules of gases, and their interactions as collisions among molecules, the equations that govern kinetic theory can be reinterpreted to model opinion dynamics in multi-agent systems. A key feature of the adopted kinetic-based approach is that it allows macroscopic properties of the system to be derived analytically. In order to take into account that the considered multi-agent system is composed of two classes of agents, kinetic theory of gas mixtures, which deals with gases composed of different kinds of molecules, is adopted. Presented results show that consensus is reached after a sufficiently large number of interactions, which depends on the parameters associated with the two classes of agents.

2016 - Interaction protocols in the JADEL programming language [Relazione in Atti di Convegno]
Bergenti, Federico; Iotti, Eleonora; Monica, Stefania; Poggi, Agostino
abstract

This paper presents the support for interaction protocols that has been recently added to the JADEL programming language. JADEL is an agent-oriented programming language designed to ease the development of JADE agents and multi-agent systems by offering general-purpose agent-oriented abstractions to the programmer. The first part of the paper presents JADEL and motivates the need for a new agent-oriented programming language. Then, the agent-oriented abstractions that JADEL has been providing since its first version-namely agents, behaviours and communication ontologies-are described. The new support for interaction protocols is finally presented, and a simple example of a JADEL multi-agent system that uses interaction protocols is reported. The paper is concluded with an overview of the current state of JADEL and related tools.

2016 - Location-aware social gaming with AMUSE [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania
abstract

This paper focuses on a novel software module that allows agents running on smart appliances to estimate their location in the physical environment thanks to an underlying ranging technology and a specific localization algorithm. The proposed module is an add-on of the AMUSE platform which allows agents to estimate their position in the physical environment and to have it readily available as a specific game element in the scope of location-aware games. The module first acquires range estimates between the appliance where the agent is running and the access points of the WiFi network, and then it properly processes such range estimates using a localization algorithm. In order to prove the validity of the proposed approach, we show experimental results obtained in an illustrative indoor scenario where four access points have been accurately positioned. The position estimates of the appliance are obtained by applying the Two-Stage Maximum-Likelihood localization algorithm to the range estimates from the four access points. According to the results presented in this paper, the proposed agent-based localization approach guarantees sufficiently accurate position estimates for many indoor applications.

2016 - Low-complexity UWB-based collision avoidance system for automated guided vehicles [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

This paper describes a low-complexity collision avoidance system for automated guided vehicles (AGVs) based on active ultra-wide band (UWB) modules. In particular, we consider an industrial warehouse where all the AGVs and target nodes (TNs) (e.g., people) are equipped with active UWB modules. A communication session between a pair of UWB modules permits the exchange of information and the estimation of the distance between them. The UWB module positioned on an AGV is connected to an on-board computer; whenever the UWB module on an AGV receives a message from a TN, it communicates all the received data to the on-board computer that can decide to stop the AGV if the range estimate is below a given threshold. This prevents undesired collisions between the AGV and the TN. In this paper, we present the experimental results of the proposed collision avoidance system obtained using the UWB modules, PulsON 410 ranging and communication modules (P410 RCMs), produced by Time Domain.

2016 - Maximum likelihood localization: When does it fail? [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

Maximum likelihood is a criterion often used to derive localization algorithms. In particular, in this paper we focus on a distance-based algorithm for the localization of nodes in static wireless networks. Assuming that Ultra Wide Band (UWB) signals are used for inter-node communications, we investigate the ill-conditioning of the Two-Stage Maximum-Likelihood (TSML) Time of Arrival (ToA) localization algorithm as the Anchor Nodes (ANs) positions change. We analytically derive novel lower and upper bounds for the localization error and we evaluate them in some localization scenarios as functions of the ANs’ positions. We show that particular ANs’ configurations intrinsically lead to ill-conditioning of the localization problem, making the TSML-ToA inapplicable. For comparison purposes, we also show, through some examples, that a Particle Swarm Optimization (PSO)-based algorithm guarantees accurate positioning also when the localization problem embedded in the TSML-ToA algorithm is ill-conditioned.

2016 - Polynomial constraint solving over finite domains with the modified Bernstein form [Relazione in Atti di Convegno]
Bergenti, Federico; Monica, Stefania; Rossi, Gianfranco
abstract

This paper describes an algorithm that can be used to effectively solve polynomial constraints over finite domains. Such constraints are expressed in terms of inequalities of polynomials with integer coefficients whose variables are assumed to be defined over proper finite domains. The proposed algorithm first reduces each constraint to a canonical form, i.e., a specific form of inequality, then it uses the modified Bernstein form of resulting polynomials to incrementally restrict the domains of variables. No approximation is involved in the solving process because the coefficients of the modified Bernstein form of the considered type of polynomials are always integer numbers.

2015 - A Kinetic Study of Opinion Dynamics in Multi-agent Systems [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

In this paper we rephrase the problem of opinion formation from a physical viewpoint. We consider a multi-agent system where each agent is associated with an opinion and interacts with any other agent. Interpreting the agents as the molecules of a gas, we model the opinion evolution according to a kinetic model based on the analysis of interactions among agents. From a microscopic description of each interaction between pairs of agents, we derive the stationary profiles under given assumption. Results show that, depending on the average opinion and on the model parameters, different profiles can be found, with different properties. Each stationary profile is characterized by the presence of one or two maxima.

2015 - A Swarm Intelligence Approach to 3D Distance-Based Indoor UWB Localization [Capitolo/Saggio]
Monica, Stefania; Ferrari, Gianluigi
abstract

In this paper, we focus on the application of Ultra Wide Band (UWB) technology to the problem of locating static nodes in three-dimensional indoor environments, assuming to know the positions of a few nodes, denoted as “beacons.” The localization algorithms which are considered throughout the paper are based on the Time Of Arrival (TOA) of signals traveling between pairs of nodes. In particular, we propose to apply the Particle Swarm Optimization (PSO) algorithm to solve the localization problem and we compare its performance with that of the Two-Stage Maximum-Likelihood (TSML) algorithm. Simulation results show that the former allows achieving accurate position estimates even in scenarios where, because of ill-conditioning problems associated with the network topology, TSML fails.

2015 - Gruppo di localizzazione di un obiettivo mobile in un magazzino con veicoli a guida automatica [Brevetto]
Monica, Stefania; Ferrari, Gianluigi; Magnani, M.; Oleari, Fabio; De Mola, F.
abstract

2015 - Kinetic Description of Opinion Evolution in Multi-agent Systems: Analytic Model and Simulations [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

In this paper we consider multi-agent systems where interactions among agents are modeled using a kinetic approach. While kinetic theory aims at studying macroscopic properties of gases starting from microscopic interactions among molecules, we are interested in modeling the global behaviour of multi-agent systems on the basis of local interactions among pairs of agents. In particular, here we study the dynamics of opinion formation. Given a microscopic description of each single interaction, we derive stationary profiles for the global opinion. Analytic results are validated by simulations obtained by implementing the proposed theoretical model.

2015 - Location-aware JADE Agents in Indoor Scenarios [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

This paper presents a novel JADE add-on that enables the implementation of location-aware agents by interfacing an underlying ranging technology which provides accurate distance measures both indoor and outdoor. First, the paper motivates the work and it presents the features and the architecture of the add-on. Then, the paper provides a detailed description of the implemented localization algorithms and it validates them in an indoor scenario. The experimental results show that accurate indoor localization can be achieved and that the presented add-on can be used to support location-aware agents with sufficient accuracy for targeted educational and ludic applications.

2015 - Simulations of Opinion Formation in Multi-Agent Systems Using Kinetic Theory [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

In this paper we formulate the problem of opinion formation using a physical metaphore. We consider a multiagent system where each agent is associated with an opinion and interacts with any other agent. Interpreting the agents as the molecules of a gas, we model the evolution of opinion in the system according to a kinetic model based on the analysis of interactions among agents. From a microscopic description of each interaction between two agents, we derive the stationary profiles of the opinion under given assumption. Results show that, depending on the average opinion and on the parameters of the model, different profiles can be found, but all stationary profiles are characterized by the presence just of one or two maxima. Analytic results are confirmed by simulations shown in the last part of the paper.

2015 - UWB-based localization in large indoor scenarios: Optimized placement of anchor nodes [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

In this paper, we consider the problem of locating a target node (TN) moving along a corridor in a large industrial environment by means of ultrawide band signaling from fixed anchor nodes (ANs) uniformly positioned at the same height on both sides of the corridor. For a representative geometry of a large indoor (industrial) scenario, we formulate an analytical approach to the optimized placement (in terms of internode distance) of ANs using the criterion of minimizing the average mean square error (MSE) in the time-difference-of-arrival-based estimated positions of the TN. Under the assumption of a fixed variance of the range estimation error, we derive a simple closed-form expression for the optimal inter-AN distance in terms of the corridor width and the height of the ANs. The effectiveness of the analytical approach is confirmed by simulations. We also show that the proposed approach allows the MSE in the TN position estimates to reach the Cramer Rao lower bound.

2014 - A Stochastic Model of Self-Stabilizing Cellular Automata for Consensus Formation [Relazione in Atti di Convegno]
Monica, Stefania; Bergenti, Federico
abstract

In this paper we present a model of the dynamics of an interesting class of stochastic cellular automata. Such automata are variants of automata used for density classification and they are chosen because they can be effectively used to address consensus problems. After introducing the topic and the basic notation, we study the dynamics of such automata by means of simulations with varying periods and neighborhood structures. We use the results of simulations to extrapolate a stochastic model of the dynamics of such automata that can be used to estimate stabilization time.

2014 - Accurate indoor localization with UWB wireless sensor networks [Relazione in Atti di Convegno]
Monica, Stefania; Ferrari, Gianluigi
abstract

Wireless Sensor Networks (WSNs) consist of a collection of spatially distributed radio transceivers with attached sensors that can measure and gather information from the environment. In this paper, we focus on the application of WSNs to indoor localization and, for this purpose, we propose the use of a Ultra Wide Band (UWB) WSN. The use of UWB signals guarantees robust performance in dense multipath environments, making them an attractive choice for indoor localization. In this paper, we discuss on different localization strategies: first classic geometric approaches are considered, then the mathematical framework is re-interpreted as an optimization problem. In the latter context, we propose the use of Particle Swarm Optimization (PSO) in particular, which can overcome limitations of classic (geometric) approaches.

2014 - An experimental model for UWB distance measurements and its application to localization problems [Relazione in Atti di Convegno]
Monica, Stefania; Ferrari, Gianluigi
abstract

The goal of this paper is to analyze the impact of an accurate statistical model for distance estimation on the localization accuracy of practical Ultra Wide Band (UWB) systems. Our experimental investigation is based on the use of a particular type of UWB sensors, namely the PulsON 410 Ranging and Communications Modules (P410 RCMs) produced by Time Domain. First, we derive a statistical model for distance estimate between pairs of UWB sensors, finding a (linear) relation between the inter-modules distance and the average distance error. Similarly, a (linear) approximation for the standard deviation of the distance error is derived. Finally, we consider four P410 RCMs: assuming to know the positions of three of them, the position of the remaining one is estimated relying on distance measurements between pairs of them. Our results show that the localization accuracy is improved taking into account the statistical model for the distance estimate derived in the first part of the paper.

2014 - Swarm intelligent approaches to auto-localization of nodes in static UWB networks [Articolo su rivista]
Monica, Stefania; Ferrari, Gianluigi
abstract

In this paper, we address the problem of localizing sensor nodes in a static network, given that the positions of a few of them (denoted as "beacons") are a priori known. We refer to this problem as "auto-localization." Three localization techniques are considered: the two-stage maximum-likelihood (TSML) method; the plane intersection (PI) method; and the particle swarm optimization (PSO) algorithm. While the first two techniques come from the communication-theoretic "world," the last one comes from the soft computing "world." The performance of the considered localization techniques is investigated, in a comparative way, taking into account (i) the number of beacons and (ii) the distances between beacons and nodes. Since our simulation results show that a PSO-based approach allows obtaining more accurate position estimates, in the second part of the paper we focus on this technique proposing a novel hybrid version of the PSO algorithm with improved performance. In particular, we investigate, for various population sizes, the number of iterations which are needed to achieve a given error tolerance. According to our simulation results, the hybrid PSO algorithm guarantees faster convergence at a reduced computational complexity, making it attractive for dynamic localization. In more general terms, our results show that the application of soft computing techniques to communication-theoretic problems leads to interesting research perspectives.

2013 - Approccio elementare alla teoria cinetica [Working paper]
Monica, S.; Bisi, M.; Groppi, M.; Spiga, G.
abstract

2013 - Auto-localization of static nodes in UWB wireless sensor networks [Relazione in Atti di Convegno]
Monica, S.; Ferrari, G.
abstract

In this paper, we focus on the auto-localization of static sensor nodes in a Wireless Sensor Network (WSN), assuming to know the position of a few of them, which will be denoted as “beacons”. Assuming that Ultra Wide Band (UWB) signals are used for inter-node communications, we compare the accuracy of the position estimates obtained by using three different algorithms, namely: the Two-Stage Maximum-Likelihood (TSML) method, the Plane Intersection (PI) method, and the Particle Swarming Optimization (PSO) algorithm. Simulation results show that a small number of beacons is sufficient to achieve an accurate position estimate when using the PSO algorithm, making it an attractive choice to implement effective localization systems.

2013 - Hybrid Swarm Intelligent Node Localization in Wireless Sensor Networks [Relazione in Atti di Convegno]
Monica, S.; Ferrari, G.
abstract

In this paper, we consider the problem of locating nodes of a Wireless Sensor Network (WSN), assuming that they communicate through Ultra Wide Band (UWB) signaling. In particular, we assume to know the exact position of a few nodes, denoted as “beacons,” and we investigate how to get the positions of other nodes in the network by means of range measurements obtained via signals exchanges between nodes. We focus on solving this problem through a swarm intelligencebased approach. In particular, we compare “classical” Particle Swarming Optimization (PSO) with a modified version of this algorithm, characterized by a faster convergence. We show that, for the considered problem, the latter gives the same performance of the first one with a smaller number of iterations.

2013 - Impact of the Number of Beacons in PSO-based Auto-localization in UWB Networks [Capitolo/Saggio]
Monica, S.; Ferrari, G.
abstract

In this paper, we focus on auto-localization of nodes in a static wireless network, under the assumption of known position of a few initial nodes, denoted as “beacons”. Assuming that Ultra Wide Band (UWB) signals are used for inter-node communications, we analyze the impact of the number of beacons on the location accuracy. Three different approaches to localization are considered, namely: the Two-Stage Maximum-Likelihood (TSML) method ; the Plane Intersection (PI) method, and Particle Swarming Optimization (PSO). Simulation results show that PSO allows to obtain accurate postion estimates with a small number of beacons, making it an attractive choice to implement effective localization algorithm.

2013 - Optimized anchors placement: an analytical approach in UWB-based TDOA localization [Relazione in Atti di Convegno]
Monica, Stefania; Ferrari, Gianluigi
abstract

In this paper, we consider the problem of locating an Automated Guided Vehicle (AGV) which moves on a plane in an industrial environment by means of Ultra-Wide Band (UWB) signaling from fixed Anchors Nodes (ANs) situated in the (threedimensional) space. An analytical approach to optimize, under proper (realistic) constraints, the placement of the ANs used to locate the AGV is proposed. Analytical results are confirmed by simulations.

2013 - Particle swarm optimization for auto-localization of nodes in wireless sensor networks [Capitolo/Saggio]
Monica, S.; Ferrari, G.
abstract

In this paper, we consider the problem of auto-localization of the nodes of a static Wireless Sensor Network (WSN) where nodes communicate through Ultra Wide Band (UWB) signaling. In particular, we investigate auto-localization of the nodes assuming to know the position of a few initial nodes, denoted as “beacons”. In the considered scenario, we compare the location accuracy obtained with the widely used Two-Stage Maximum-Likelihood algorithm with that achieved with an algorithm based on Particle Swarming Optimization (PSO). Accurate simulation results show that the latter can significantly outperform the former.

2012 - An analytical approach to optimized anchors placement in UWB-based indoor localization [Relazione in Atti di Convegno]
Monica, S.; Ferrari, G.
abstract

In this paper, we consider the problem of locating an Automated Guided Vehicle (AGV) in an industrial environment by means of Ultra-Wide Band (UWB) signaling from fixed Anchors Nodes (ANs). We derive a novel analytical approach to optimize, under proper (realistic) constraints, the placement of the ANs used to locate the AGV. Analytical results are confirmed by simulations.

2011 - A kinetic ellipsoidal BGK model for a binary gas mixture [Articolo su rivista]
Groppi, M.; Monica, S.; Spiga, G.
abstract

Università degli studi di Modena e Reggio Emilia

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