In the application of software intensive systems to business-critical processes, tool-supported c... more In the application of software intensive systems to business-critical processes, tool-supported connection between the perspectives of Software Engineering and Reliability Engineering may largely help conciliation of the contrasting needs of reliability and complexity. In this paper, we present FaultFlow, a newborn tool enabling a Model-Driven Engineering approach for supporting specification, analysis, and simulation of failure logic in component-based systems. The tool exploits a meta-model combining the representation of system configuration hierarchies together with a decoupled representation of its stochastically-timed failure logic. FaultFlow is available in a as-a-service mode through a Web Application deployed on the cloud as well as in a standalone mode, featuring a well-crafted Java API enabling effective specification of the system hierarchy as well as of intra-component fault-to-failure and inter-component failure-to-fault propagation models, respectively starting from SysML Block Definition Diagrams and stochastic Fault Trees representations. The automated transformation towards Stochastic Time Petri Nets enables integration with external reliability tools for quantitative evaluation through numerical solution or simulation. We illustrate FaultFlow key benefits by experimenting the approach on a case study contextualised in an Internet of Things scenario modelling a Pollution Monitor System within a Smart City.
A visual formalism for the presentation of a real time logic is introduced, motivated, and evalua... more A visual formalism for the presentation of a real time logic is introduced, motivated, and evaluated.The visual formalism has been designed following a user-centered usability engineering process, targeted to the students of higher education courses in software engineering. On the one hand, heuristic design was applied to maximize consistency, i.e. to minimize the complexity of the visual metaphor mapping textual sentences to the visual representation. On the other hand, individual metaphoric assumptions were defined by prototyping and exposing alternative graphical representations to a representative sample of the target community of expected users.The resulting notation has been implemented within an interactive syntax-directed editor which integrates the visual presentation with the conventional textual notation. The editor has been used to carry out a competitive user-based evaluation of the usability of textual and visual representations, by carrying out a readability test on a larger sample of representative end-users.
Medical Informatics and The Internet in Medicine, 1999
In the evaluation of regional left ventricular function, relevant cardiac disorders manifest them... more In the evaluation of regional left ventricular function, relevant cardiac disorders manifest themselves not only in static features, such as shape descriptors and motion excursion in end-diastolic and end-systolic frames, but also in their temporal evolution. In common diagnostic practice, such dynamic patterns are analysed by direct inspection of frame sequences through the use of a moviola. This permits only a subjective and poorly defined evaluation of functional parameters, and definitely prevents a systematic and reproducible analysis of large sets of reports. Retrieval by contents techniques may overcome this limitation by permitting the automatic comparison of the reports in a database against queries expressing descriptive properties related to significant pathological conditions. A system is presented which is aimed at investigating the potential of this approach by supporting retrieval by contents from a database of cineangiographic or echocardiographic images. The system relies on a symbolic description of both geometrical and temporal properties of left ventricular contours. This is derived automatically by an image processing and interpretation module and associated with the report at its storage time. In the retrieval stage, queries are expressed by means of an iconic visual language which describes searched content properties over a computer screen. The system automatically interprets iconic statements and compares them against concrete descriptions in the database. This enables medical users to interact with the system to search for motion and shape abnormalities on a regional basis, in single or homogeneous groups of reports, so as to enable both prospective and retrospective diagnosis.
ORIS provides a graphical interface to draw Petri nets, analysis engines for different classes of... more 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 transient analysis of Semi-Markov Processes (SMPs), Markov Regenerative Processes (MRPs), Generalized Semi-Markov Processes (GSMPs), and Continuous-Time Markov Chains (CTMCs).
ORIS is a tool for quantitative modeling and evaluation of concurrent systems with non-Markovian ... more 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 provides an open-source Java Application Programming Interface (API) to automate the workflow, and it can be used as a toolkit for derivation and evaluation of STPNs in model driven engineering. As distinguishing features, ORIS implements transient and steady-state analysis of STPNs with underlying Markov Regenerative Process (MRP), and transient analysis of STPNs with underlying Generalized Semi- Markov Process (GSMP). It also implements nondeterministic analysis of Time Petri Nets (TPNs), simulation of STPNs, and solution methods for Continuous-Time Markov Chains (CTMCs) and MRPs with at most one non-exponential timer in each state. The well-engineered software architecture of ORIS supports agile implementation of new STPN features, new modeling formalisms, and new analysis methods.
Agile production systems face major issues in satisfying fickle market needs in highly demand-dri... more Agile production systems face major issues in satisfying fickle market needs in highly demand-driven industry sectors, such as electronics and mechatronics. In this context, the time needed to complete the production of an item tends to be highly variable, and online estimation of the remaining completion time may suffer the lack of adequate sensor data, especially in existing manufacturing systems. To solve this issue, we propose a new analytical technique for the evaluation of an upper and a lower stochastic bound on the remaining completion time of a product, considering an assembly line made of sequential workstations with transfer blocking and buffer capacity. The approach notably encompasses service times with non-Markovian distribution, and avoids the limitation of existing works requiring the system to be at steady state at the inspection time. The technique is experimented on a case study and validated through simulation, providing an empirical analysis of its complexity.
Transient analysis of Markov Regenerative Processes (MRPs) can be performed through the solution ... more 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 methods exclusively address the case where at most one generallydistributed timer is enabled in each state, or where regenerations occur in a bounded number of events. In this work, we analyze the state space of the underlying timed model to identify epochs between regenerations and apply distinct methods to each epoch depending on the satisfied conditions. For epochs not amenable to existing methods, we propose an adaptive approximation of kernel entries based on partial exploration of the state space, leveraging heuristics that permit to reduce the error on transient probabilities. The case study of a polling system with generallydistributed service times illustrates the effect of these heuristics and how the approach extends the class of models that can be analyzed.
Extreme weather events such as heavy rains and floods are becoming more frequent and severe due t... more 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 on public health. They can be cast in the class of cyber-physical systems, since their operation is governed by their physical behaviour-related to topology, fluid-dynamics and technology-which in turn is steered by operation policies and user behaviour-pump and valve management, demand-response mechanisms, etc. In this context, we propose an approach to estimate resilience in the indirect damage caused by a flood on a Water Supply System (WSS). To this end, we combine analysis of an inundation model, which computes the floodwater depth over time on the studied territory, and evaluation of a hydraulic network model by a Pressure-Driven Demand (PDD) approach, which also allows for demand-response mechanisms. Flood damage is assessed in terms of both lack of service experienced by inhabitants and length of pipeworks contam
Background: In order to remain active and productive, older adults with poor health require a com... more Background: In order to remain active and productive, older adults with poor health require a combination of advanced methods of visual monitoring, optimization, pattern recognition, and learning, which provide safe and comfortable environments and serve as a tool to facilitate the work of family members and workers, both at home and in geriatric homes. Therefore, there is a need to develop technologies to provide these adults autonomy in indoor environments. Objective: This study aimed to generate a prediction model of daily living activities through classification techniques and selection of characteristics in order to contribute to the development in this area of knowledge, especially in the field of health. Moreover, the study aimed to accurately monitor the activities of the elderly or people with disabilities. Technological developments allow predictive analysis of daily life activities, contributing to the identification of patterns in advance in order to improve the quality ...
Intelligent Transportation Systems for urban mobility aim at the grand objective of reducing envi... more Intelligent Transportation Systems for urban mobility aim at the grand objective of reducing environmental impact and minimize urban congestion, also integrating different mobility modes and solutions. However, the different transportation modalities may end in a conflict due to physical constraints concerned with the urban structure itself: an example is the case of intersection between a public road and a tramway right-of-way, where traffic lights priority given to trams may trigger road congestion, while an intense car traffic can impact on trams’ performance. These situations can be anticipated and avoided by accurately modeling and analyzing the possible congestion events. Typically, modeling tools provide simulation facilities, by which various scenarios can be played to understand the response of the intersection to different traffic loads. While supporting early verification of design choices, simulation encounters difficulties in the evaluation of rare events. Only modeling...
Analysis of hierarchical semi-Markov processes with parallel regions is a technique that evaluate... more Analysis of hierarchical semi-Markov processes with parallel regions is a technique that evaluates steady-state probabilities of models with multiple concurrent non-Markovian timers in a compositional way without the need of full state space generation. In this paper we extend the technique by removing some of its limitations and increasing its modelling power. By applying the time advancement mechanism known from stochastic state classes, exits in parallel regions with different time origins can be taken into account. Furthermore, exits can be put on state borders such that the model evolution depends on the exited region and a concept for history states is also presented. This significantly increases modeling power, such that the gap between semi-Markov processes with restricted modeling power and non-Markovian models without modeling restrictions but also with less efficient analysis is filled. Experimentations in order to validate the approach and to compare it with another technique were performed in order to better characterise the advantages of the compositional approach.
We present a model-based approach to performance evaluation of a collection of similar systems ba... more 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 buering capacity, implementing complex workows with random choices and sequential/cyclic phases with generally distributed durations and no internal parallelism. Starting from the steady state, an inspection mechanism is subject to some degree of uncertainty in the identication of the current phase of each workstation, and is in any case unable to estimate remaining times. By relying on the positive correlation between delays at dierent workstations, we provide stochastic upper and lower approximations of the performance measures of interest, including the time to completion of the local workow of each workstation and the time until when a workstation starts a new job. Experimental results show that the approximated evaluation is accurate and feasible for lines of signicant complexity.
In the application of software intensive systems to business-critical processes, tool-supported c... more In the application of software intensive systems to business-critical processes, tool-supported connection between the perspectives of Software Engineering and Reliability Engineering may largely help conciliation of the contrasting needs of reliability and complexity. In this paper, we present FaultFlow, a newborn tool enabling a Model-Driven Engineering approach for supporting specification, analysis, and simulation of failure logic in component-based systems. The tool exploits a meta-model combining the representation of system configuration hierarchies together with a decoupled representation of its stochastically-timed failure logic. FaultFlow is available in a as-a-service mode through a Web Application deployed on the cloud as well as in a standalone mode, featuring a well-crafted Java API enabling effective specification of the system hierarchy as well as of intra-component fault-to-failure and inter-component failure-to-fault propagation models, respectively starting from SysML Block Definition Diagrams and stochastic Fault Trees representations. The automated transformation towards Stochastic Time Petri Nets enables integration with external reliability tools for quantitative evaluation through numerical solution or simulation. We illustrate FaultFlow key benefits by experimenting the approach on a case study contextualised in an Internet of Things scenario modelling a Pollution Monitor System within a Smart City.
A visual formalism for the presentation of a real time logic is introduced, motivated, and evalua... more A visual formalism for the presentation of a real time logic is introduced, motivated, and evaluated.The visual formalism has been designed following a user-centered usability engineering process, targeted to the students of higher education courses in software engineering. On the one hand, heuristic design was applied to maximize consistency, i.e. to minimize the complexity of the visual metaphor mapping textual sentences to the visual representation. On the other hand, individual metaphoric assumptions were defined by prototyping and exposing alternative graphical representations to a representative sample of the target community of expected users.The resulting notation has been implemented within an interactive syntax-directed editor which integrates the visual presentation with the conventional textual notation. The editor has been used to carry out a competitive user-based evaluation of the usability of textual and visual representations, by carrying out a readability test on a larger sample of representative end-users.
Medical Informatics and The Internet in Medicine, 1999
In the evaluation of regional left ventricular function, relevant cardiac disorders manifest them... more In the evaluation of regional left ventricular function, relevant cardiac disorders manifest themselves not only in static features, such as shape descriptors and motion excursion in end-diastolic and end-systolic frames, but also in their temporal evolution. In common diagnostic practice, such dynamic patterns are analysed by direct inspection of frame sequences through the use of a moviola. This permits only a subjective and poorly defined evaluation of functional parameters, and definitely prevents a systematic and reproducible analysis of large sets of reports. Retrieval by contents techniques may overcome this limitation by permitting the automatic comparison of the reports in a database against queries expressing descriptive properties related to significant pathological conditions. A system is presented which is aimed at investigating the potential of this approach by supporting retrieval by contents from a database of cineangiographic or echocardiographic images. The system relies on a symbolic description of both geometrical and temporal properties of left ventricular contours. This is derived automatically by an image processing and interpretation module and associated with the report at its storage time. In the retrieval stage, queries are expressed by means of an iconic visual language which describes searched content properties over a computer screen. The system automatically interprets iconic statements and compares them against concrete descriptions in the database. This enables medical users to interact with the system to search for motion and shape abnormalities on a regional basis, in single or homogeneous groups of reports, so as to enable both prospective and retrospective diagnosis.
ORIS provides a graphical interface to draw Petri nets, analysis engines for different classes of... more 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 transient analysis of Semi-Markov Processes (SMPs), Markov Regenerative Processes (MRPs), Generalized Semi-Markov Processes (GSMPs), and Continuous-Time Markov Chains (CTMCs).
ORIS is a tool for quantitative modeling and evaluation of concurrent systems with non-Markovian ... more 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 provides an open-source Java Application Programming Interface (API) to automate the workflow, and it can be used as a toolkit for derivation and evaluation of STPNs in model driven engineering. As distinguishing features, ORIS implements transient and steady-state analysis of STPNs with underlying Markov Regenerative Process (MRP), and transient analysis of STPNs with underlying Generalized Semi- Markov Process (GSMP). It also implements nondeterministic analysis of Time Petri Nets (TPNs), simulation of STPNs, and solution methods for Continuous-Time Markov Chains (CTMCs) and MRPs with at most one non-exponential timer in each state. The well-engineered software architecture of ORIS supports agile implementation of new STPN features, new modeling formalisms, and new analysis methods.
Agile production systems face major issues in satisfying fickle market needs in highly demand-dri... more Agile production systems face major issues in satisfying fickle market needs in highly demand-driven industry sectors, such as electronics and mechatronics. In this context, the time needed to complete the production of an item tends to be highly variable, and online estimation of the remaining completion time may suffer the lack of adequate sensor data, especially in existing manufacturing systems. To solve this issue, we propose a new analytical technique for the evaluation of an upper and a lower stochastic bound on the remaining completion time of a product, considering an assembly line made of sequential workstations with transfer blocking and buffer capacity. The approach notably encompasses service times with non-Markovian distribution, and avoids the limitation of existing works requiring the system to be at steady state at the inspection time. The technique is experimented on a case study and validated through simulation, providing an empirical analysis of its complexity.
Transient analysis of Markov Regenerative Processes (MRPs) can be performed through the solution ... more 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 methods exclusively address the case where at most one generallydistributed timer is enabled in each state, or where regenerations occur in a bounded number of events. In this work, we analyze the state space of the underlying timed model to identify epochs between regenerations and apply distinct methods to each epoch depending on the satisfied conditions. For epochs not amenable to existing methods, we propose an adaptive approximation of kernel entries based on partial exploration of the state space, leveraging heuristics that permit to reduce the error on transient probabilities. The case study of a polling system with generallydistributed service times illustrates the effect of these heuristics and how the approach extends the class of models that can be analyzed.
Extreme weather events such as heavy rains and floods are becoming more frequent and severe due t... more 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 on public health. They can be cast in the class of cyber-physical systems, since their operation is governed by their physical behaviour-related to topology, fluid-dynamics and technology-which in turn is steered by operation policies and user behaviour-pump and valve management, demand-response mechanisms, etc. In this context, we propose an approach to estimate resilience in the indirect damage caused by a flood on a Water Supply System (WSS). To this end, we combine analysis of an inundation model, which computes the floodwater depth over time on the studied territory, and evaluation of a hydraulic network model by a Pressure-Driven Demand (PDD) approach, which also allows for demand-response mechanisms. Flood damage is assessed in terms of both lack of service experienced by inhabitants and length of pipeworks contam
Background: In order to remain active and productive, older adults with poor health require a com... more Background: In order to remain active and productive, older adults with poor health require a combination of advanced methods of visual monitoring, optimization, pattern recognition, and learning, which provide safe and comfortable environments and serve as a tool to facilitate the work of family members and workers, both at home and in geriatric homes. Therefore, there is a need to develop technologies to provide these adults autonomy in indoor environments. Objective: This study aimed to generate a prediction model of daily living activities through classification techniques and selection of characteristics in order to contribute to the development in this area of knowledge, especially in the field of health. Moreover, the study aimed to accurately monitor the activities of the elderly or people with disabilities. Technological developments allow predictive analysis of daily life activities, contributing to the identification of patterns in advance in order to improve the quality ...
Intelligent Transportation Systems for urban mobility aim at the grand objective of reducing envi... more Intelligent Transportation Systems for urban mobility aim at the grand objective of reducing environmental impact and minimize urban congestion, also integrating different mobility modes and solutions. However, the different transportation modalities may end in a conflict due to physical constraints concerned with the urban structure itself: an example is the case of intersection between a public road and a tramway right-of-way, where traffic lights priority given to trams may trigger road congestion, while an intense car traffic can impact on trams’ performance. These situations can be anticipated and avoided by accurately modeling and analyzing the possible congestion events. Typically, modeling tools provide simulation facilities, by which various scenarios can be played to understand the response of the intersection to different traffic loads. While supporting early verification of design choices, simulation encounters difficulties in the evaluation of rare events. Only modeling...
Analysis of hierarchical semi-Markov processes with parallel regions is a technique that evaluate... more Analysis of hierarchical semi-Markov processes with parallel regions is a technique that evaluates steady-state probabilities of models with multiple concurrent non-Markovian timers in a compositional way without the need of full state space generation. In this paper we extend the technique by removing some of its limitations and increasing its modelling power. By applying the time advancement mechanism known from stochastic state classes, exits in parallel regions with different time origins can be taken into account. Furthermore, exits can be put on state borders such that the model evolution depends on the exited region and a concept for history states is also presented. This significantly increases modeling power, such that the gap between semi-Markov processes with restricted modeling power and non-Markovian models without modeling restrictions but also with less efficient analysis is filled. Experimentations in order to validate the approach and to compare it with another technique were performed in order to better characterise the advantages of the compositional approach.
We present a model-based approach to performance evaluation of a collection of similar systems ba... more 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 buering capacity, implementing complex workows with random choices and sequential/cyclic phases with generally distributed durations and no internal parallelism. Starting from the steady state, an inspection mechanism is subject to some degree of uncertainty in the identication of the current phase of each workstation, and is in any case unable to estimate remaining times. By relying on the positive correlation between delays at dierent workstations, we provide stochastic upper and lower approximations of the performance measures of interest, including the time to completion of the local workow of each workstation and the time until when a workstation starts a new job. Experimental results show that the approximated evaluation is accurate and feasible for lines of signicant complexity.
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Papers by Enrico Vicario