Laura Carnevali

Laura Carnevali
University of Florence | UNIFI · Dipartimento di Ingegneria dell'Informazione

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54
Publications
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483
Citations

Publications

Publications (54)
Chapter
We present Eulero, a novel Java library enabling modeling of complex workflows and evaluation of their end-to-end response time Probability Density Function (PDF). Workflows consist of activities with general (i.e., non-exponential) duration with bounded support, composed through sequence, choice/merge, and split/join blocks, with unbalanced split...
Article
ORIS is a tool for quantitative modeling and evaluation of concurrent systems with non-Markovian durations. It provides a Graphical User Interface (GUI) for model specification as Stochastic Time Petri Nets (STPNs), validation by interactive simulation, and evaluation by several techniques, computing instantaneous and cumulative rewards. It also pr...
Article
Quantitative evaluation of stochastic models supports early verification of design choices and assessment of non-functional requirements. Model Driven Engineering~(MDE) leverages automated derivation of formal stochastic models from semi-formal artifacts \tc{of} the Unified Modeling Language~(UML) to facilitate deployment of quantitative evaluation...
Book
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The Artistic goods represent a priceless asset of our cultural patrimony since they play a crucial role in defining and understanding the identity of communities. Nevertheless, they are not always adequately protected against possible dangers and hazards or the effects of time. In these last decades, the new technologies - such as the digital contr...
Chapter
We propose a compositional technique for efficient evaluation of the cumulative distribution function of the response time of complex workflows, consisting of activities with generally distributed stochastic durations composed through sequence, choice/merge, split/join, and repetition blocks, with unbalanced split and join constructs that break the...
Article
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Reliability Block Diagrams (RBDs) are widely used in reliability engineering to model how the system reliability depends on the reliability of components or subsystems. In this paper, we present librbd, a C library providing a generic, efficient and open-source solution for time-dependent reliability evaluation of RBDs. The library has been develop...
Article
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Predictive diagnosis of wheel wear plays a fundamental role in maintenance of railway vehicles. While on-board installation of wear sensors is affordable only for modern high-performance trains (e.g., high-speed trains), evaluation of wheel wear is mostly performed through periodic measures in maintenance sites for low-performance trains (e.g., sec...
Article
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In the last decades, the socio-demographic evolution of the population has substantially changed mobility demand, posing new challenges in minimizing urban congestion and reducing environmental impact. In this scenario, understanding how different modes of transport can efficiently share (partially or totally) a common infrastructure is crucial for...
Article
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In systems with imperfect fault coverage (IFC), all components are subject to uncovered failures, possibly threatening the whole system. Therefore, to improve the system reliability, it is important to timely detect, identify, and shut down the components that are no more relevant for the system operation. This article addresses quantitative evalua...
Article
We present the next generation of ORIS, a toolbox for quantitative evaluation of concurrent models with non-Markovian timers. The tool shifts the focus from timed models to stochastic ones: it includes a new graphical user interface, new analysis methods and a Java Application Programming Interface (API). Models can be specified as Stochastic Time...
Article
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We present a model-based approach to Activity Recognition (AR) in Ambient Assisted Living (AAL). The approach leverages an a priori stochastic model termed Continuous-Time Hidden Semi-Markov Model (CT-HSMM), capturing the continuous-time durations of activities and inter-event times. The model is enhanced according to the observed statistics, assoc...
Chapter
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Extreme weather events such as heavy rains and floods are becoming more frequent and severe due to global warming, therefore leading to an increasing interest in methods to evaluate environmental consequences and mitigation strategies. Water supply systems (WSS) represent a class of safety-critical infrastructure prone to damage, with direct impact...
Article
We propose an approach for assessing the impact of multi-phased repair procedures on gas distribution networks, capturing load profiles that can depend on time for different classes of users, suspension of activities during non-working hours, and random execution times depending on topological, physical, and geographical characteristics of the netw...
Article
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A Water Distribution System (WDS) is a critical infrastructure for society and economy, subject to frequent maintenance either for contingencies or planned operations. Maintenance procedures affect the hybrid dynamics of a WDS at stochastic time points, representing the completion of repair activities that change the WDS topology and operation mode...
Conference Paper
Full-text available
ORIS provides a graphical interface to draw Petri nets, analysis engines for different classes of underlying stochastic process, and visualization of reward-based metrics. It also includes a Java API for model definition and analysis, which can be used to carry out parametric performance studies. ORIS implements methods for steady-state and transie...
Article
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Level 3 of the ERTMS/ETCS improves the capacity of railways by replacing fixed-block signalling, which prevents a train to enter a block occupied by another train, with moving block signalling, which allows a train to proceed as long as it receives radio messages ensuring that the track ahead is clear of other trains. If messages are lost, a train...
Conference Paper
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We present a model-based approach to performance evaluation of a collection of similar systems based on runtime observations. As a concrete example, we consider an assembly line made of sequential workstations with transfer blocking and no buffering capacity, implementing complex workflows with random choices and sequential/cyclic phases with gener...
Conference Paper
Transient analysis of Markov Regenerative Processes (MRPs) can be performed through the solution of Markov renewal equations defined by global and local kernels, which respectively characterize the occurrence of regenerations and transient probabilities between them. To derive kernels from stochastic models (e.g., stochastic Petri nets), existing m...
Chapter
Disaster victim evacuation is one of the most urgent disaster relief efforts in saving lives after a disaster strikes a populated area. In urban areas, candidate routes to take for evacuation are basically determined based on static hazard maps depending on the types of disasters (e.g., routes which are not in areas at risk of landslide disaster in...
Conference Paper
In a variety of contexts, time-stamped and typed event logs enable the construction of a stochastic model capturing the sequencing and timing of observable discrete events. This model can serve various objectives including: diagnosis of the current state; prediction of its evolution over time; scheduling of response actions. We propose a technique...
Conference Paper
In Ambient Assisted Living (AAL), Activity Recognition (AR) plays a crucial role in filling the semantic gap between sensor data and interpretation needed at the application level. We propose a quantitative model-based approach to on-line prediction of activities that takes into account not only the sequencing of events but also the continuous dura...
Conference Paper
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The European Rail Traffic Management System/European Train Control System (ERTMS/ETCS) is an innovative standard introduced to enhance reliability, safety, performance, and interoperability of trans-European railways. In Level 3, the standard replaces fixed-block safety mechanisms, in which only one train at a time is allowed to be in each railway...
Article
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The infrastructures used in cities to supply power, water and gas are consistently becoming more automated. As society depends critically on these cyber-physical infrastructures, their survivability assessment deserves more attention. In this overview, we first touch upon a taxonomy on survivability of cyber-physical infrastructures, before we focu...
Conference Paper
Quantitative evaluation of real-time systems demands for analysis frameworks that go beyond worst-case assumptions, since some parameters could be better characterized by a random variable than by a deterministic value. On the one hand, this opens notable issues on the safe estimation of probabilistic parameters starting from real measurements. On...
Conference Paper
Full-text available
Gas networks comprise a special class of infrastructure, with relevant implications on safety and availability of universal services. In this context, the ongoing deregulation of network operation gives relevance to modeling and evaluation techniques supporting predictability of dependability metrics. We propose a modeling approach that represents...
Conference Paper
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We present models and metrics for the survivability assessment of distribution power grid networks accounting for the impact of multiple failures due to large storms. The analytical models used to compute the proposed metrics are built on top of three design principles: state space factorization, state aggregation, and initial state conditioning. U...
Conference Paper
Rising competition among gas distribution companies, grow- ing availability of smart metering devices, and increasingly strict requirements on agreed service levels stimulate re- search on advanced modeling and solution techniques for quantitative evaluation of gas distribution networks. We propose a novel methodology for modeling and evaluation of...
Article
Full-text available
We present an approach for integration of formal methods within an industrial SW process, illustrating results obtained in a real scenario subject to Military Standard 498 (MIL-STD-498). On the one hand, the formal nucleus of preemptive Time Petri Nets (pTPNs) is used to support design and verification activities of the development process; on the...
Conference Paper
When software contains aging-related faults and the system has a long mission period, phased-mission systems consisting of several software components can suffer from software aging, which is a progressive degradation of the software execution environment. Failures caused by software aging might impact on the mission success probability. In this pa...
Conference Paper
Full-text available
The concept of Phased Mission Systems (PMS) can be used to describe maintenance procedures made of sequential actions that use a set of resources and may severely affect them, for instance operations that require outage of hardware and/or software components to recover from a failure or to perform upgrades, tests, and configuration changes. We prop...
Article
Full-text available
Hierarchical Scheduling (HS) techniques achieve resource partitioning among a set of real-time applications, providing reduction of complexity, confinement of failure modes, and temporal isolation among system applications. This facilitates compositional analysis for architectural verification and plays a crucial role in all industrial areas where...
Conference Paper
Quantitative evaluation of models with stochastic timings can decisively support schedulability analysis and performance engineering of real-time concurrent systems. These tasks require modeling formalisms and solution techniques that can encompass stochastic temporal parameters firmly constrained within a bounded support, thus breaking the limits...
Article
Full-text available
In the process of testing of concurrent timed systems, input generation identifies values of temporal parameters that let the Implementation Under Test (IUT) execute selected cases. However, when some parameters are not under control of the driver, test execution may diverge from the selected input and produce an inconclusive behavior. We formulate...
Article
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Preemptive Time Petri Nets (pTPNs) support modeling and analysis of concurrent timed SW components running under fixed priority preemptive scheduling. The model is supported by a well-established theory based on symbolic state space analysis through Difference Bounds Matrix (DBM) zones, with specific contributions on compositional modularization, t...
Conference Paper
Full-text available
Sirio is a framework for simulation and symbolic analysis of preemptive and stochastic extensions of Time Petri Nets (TPNs), enabling an integrated approach to correctness verification and quantitative evaluation of timed concurrent systems. In particular, it supports evaluation of transient and steady-state reward measures, both through simulation...
Conference Paper
Full-text available
Hierarchical Scheduling (HS) systems manage a set of real-time applications through a scheduling hierarchy, enabling partitioning and reduction of complexity, confinement of failure modes, and temporal isolation among system applications. This plays a crucial role in all industrial areas where high-performance microprocessors allow growing integrat...
Conference Paper
The method of stochastic state classes provides a means for quantitative analysis of a rather wide class of non-Markovian models. As a major and structural limitation, the approach cannot be applied to models encompassing a preemptive policy, which in the practice rules out the mechanism of suspension and resume usually applied in many real-time sy...
Article
Full-text available
Oris is a tool for qualitative verification and quantitative evaluation of reactive timed systems, which supports modeling and analysis of various classes of timed extensions of Petri Nets. As most characterizing features, Oris implements symbolic state space analysis of preemptive Time Petri Nets, which enable schedulability analysis of real-time...
Article
Full-text available
In the verification of reactive systems with nondeterministic densely valued temporal parameters, the state-space can be covered through equivalence classes, each composed of a discrete logical location and a dense variety of clock valuations encoded as a difference bounds matrix (DBM). The reachability relation among such classes enables qualitati...
Conference Paper
Full-text available
Critical systems require supervising infrastructures to keep their unreliability under control. We propose safety-critical systems to be modeled through a fault-tolerant architecture based on Stochastic Fault Trees (SFTs) and we refer to a scenario where the monitoring infrastructure is a Wireless Sensor Network (WSN). SFTs associate the failure ti...
Conference Paper
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We address the problem of rapid development of complex real-time task-sets through a Model Driven De- velopment (MDD) approach. The task-set is specified according to the graphic formalism of timeline schemas and it is translated into C-code that implements the dynamic architecture of the task-set on top of Linux- RTAI operating system. The transfo...
Article
Quantitative evaluation of models with generally-distributed transitions requires analysis of non-Markovian processes that may be not isomorphic to their underlying untimed models and may include any number of concurrent non-exponential timers. The analysis of stochastic Time Petri Nets copes with the problem by covering the state space with stocha...
Article
Full-text available
We propose an extension of Time Petri Nets (TPNs) that introduces a partial stochastic characterization of timers, providing a model that regards controllable and non-controllable timers as non-deterministic and stochastic variables, respectively. This induces a partial stochastic characterization of timings in the symbolic state space of the model...
Conference Paper
Full-text available
Fault Trees are widely employed in the industrial practice to support safety and reliability analysis. Various works have improved the classic formulation by replacing fixed probabilities of leaf events with Markovian distributions over time. We present operation principles, user interface and implementation architecture of a tool supporting editin...
Conference Paper
Full-text available
We describe a methodology that embeds the theory of pre- emptive Time Petri Nets (pTPN) along development and verification activities of a V-Model lifecycle to support the construction of concur- rent real time SW components. Design activities leverage on a pTPN specification of the set of concurrent timed tasks. This supports design validation thr...
Conference Paper
Full-text available
We address the problem of test case selection and path sensitization in the process of testing real-time preemptive systems, following a formal methodology based on the theory of preemptive Time Petri Nets (pTPN) implemented in the Oris tool. We discuss practical factors that limit feasible behaviors in the implementation of a nondeterministic spec...
Conference Paper
We describe a methodology for the construction of real-time tasking sets, which smoothly integrates a formal approach in both development and verification processes of the software life cycle. In the design stage, a timeline schema is used to specify concurrent processes with their dependencies and their expected temporal parameters. The schema is...

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