145 research outputs found
Strategies for the use of data and algorithm approaches in railway traffic management
Resonate are interested in looking at different strategies / models / techniques for dealing with the problem of rescheduling a railway timetable when it's unexpectedly disrupted, the likely strengths and risks of these, and how they might be adapted to improve existing solutions. Nine different approaches (drawn from machine learning, network models and stochastic models) to defining the efficiency of a station in dissipating delays were considered. They fell broadly into two groups: those that sought to understand the propagation of delays and those that sought to offer strategies for minimising delays
Risk assessment of complex engineering project based on fuzzy Petri net under the perspective of vulnerability
Traditional engineering risk management has been unable to adapt to the complexity and variability due to its constituent elements and dynamic nature of internal and external environments. Vulnerability, as a concept closely related to risk, has been neglected in the traditional risk management due to its hidden characteristics. This study attempts to quantify and evaluate vulnerabilities of complex engineering projects independently and explore the transmission mechanism between risk and vulnerability factors. Twenty different types of large-scale engineering projects in China were selected as case studies from the Mega Project Case Study Center (MPCSC) of Tongji University. Vulnerability and risk factors of each project were identified and analysed. A mechanism model was developed to explore the impacts of vulnerabilities and risks through ta Fuzzy Petri Net. Four main vulnerability-risk critical paths were identified through the reverse labelling method. The overall evaluation of engineering project risks considering the impacts of vulnerabilities is the highlight of this paper. This study interprets the cognition and evaluation of complex engineering risks from a new perspective, enriches the connotation of engineering risk management, and provides a reference for risk management and decisionmaking of complex engineering projects
Fiabilité opérationnelle des avoins (Approche basée sur les modèles et cas d'étude)
Lors de la conception des avions, il est courant que les constructeurs évaluent la sûreté de fonctionnement en utilisant des modèles stochastiques, mais l'évaluation de la fiabilité opérationnelle à l aide de modèles en ligne, pendant la réalisation des missions, reste rarement effectuée. Souvent, l'évaluation stochastique concerne la sécurité des avions. Cette thèse porte sur la modélisation de la fiabilité opérationnelle des avions, pour aider à la planification des activités de maintenance et des missions, ainsi qu à la bonne réalisation de ces dernières. Nous avons développé une approche de modélisation, basée sur un méta-modèle qui sert de base i) de structuration des informations nécessaires à l évaluation de la fiabilité opérationnelle d un avion et ii) pour la construction de modèles stochastiques pouvant être mis à jour dynamiquement. La mise à jour concerne l'état courant des systèmes avion, un profil de mission et les moyens de maintenance disponibles dans les diverses escales incluses dans le profil de la mission. L'objectif est de permettre l'évaluation de la fiabilité opérationnelle en ligne. Deux cas d études, basés sur des sous-systèmes avion, sont considérés à titre d'illustration. Nous présentons des exemples de résultats qui montrent le rôle important de l évaluation de la fiabilité opérationnelle pendant une mission d avionDependability assessment, by system manufacturer, during aircraft design, based on stochastic modeling, is of common practice, but model based operational dependability assessment online, during missions' achievement, is seldom done. Usually, the stochastic assessment addresses aircraft safety.This thesis addresses aircraft operational dependability modeling to support mission and maintenance planning, as well as the achievement of the missions. We develop a modeling approach, based on a meta-model that is used as a basis i) to structure the information needed to assess aircraft operational reliability and ii) to build a stochastic model that can be updated dynamically. The update concerns the current state of the aircraft system, a mission profile and the maintenance facilities available at the flight stop locations involved in the mission. The aim is to enable operational reliability assessment online. Two case studies, based on aircraft subsystems, are considered for illustration. We present examples of evaluation results that show the valuable role of operational dependability assessment during aircraft missionTOULOUSE-INSA-Bib. electronique (315559905) / SudocSudocFranceF
Tackling Dierent Business Process Perspectives
Business Process Management (BPM) has emerged as a discipline to design, control, analyze, and optimize business operations. Conceptual models lie at the core of BPM. In particular, business process models have been taken up by organizations as a means to describe the main activities that are performed to achieve a specific business goal. Process models generally cover different perspectives that underlie separate yet interrelated representations for analyzing and presenting process information. Being primarily driven by process improvement objectives, traditional business process modeling languages focus on capturing the control flow perspective of business processes, that is, the temporal and logical coordination of activities. Such approaches are usually characterized as \u201cactivity-centric\u201d. Nowadays, activity-centric process modeling languages, such as the Business Process Model and Notation (BPMN) standard, are still the most used in practice and benefit from industrial tool support. Nevertheless, evidence shows that such process modeling languages still lack of support for modeling non-control-flow perspectives, such as the temporal, informational, and decision perspectives, among others. This thesis centres on the BPMN standard and addresses the modeling the temporal, informational, and decision perspectives of process models, with particular attention to processes enacted in healthcare domains. Despite being partially interrelated, the main contributions of this thesis may be partitioned according to the modeling perspective they concern. The temporal perspective deals with the specification, management, and formal verification of temporal constraints. In this thesis, we address the specification and run-time management of temporal constraints in BPMN, by taking advantage of process modularity and of event handling mechanisms included in the standard. Then, we propose three different mappings from BPMN to formal models, to validate the behavior of the proposed process models and to check whether they are dynamically controllable. The informational perspective represents the information entities consumed, produced or manipulated by a process. This thesis focuses on the conceptual connection between processes and data, borrowing concepts from the database domain to enable the representation of which part of a database schema is accessed by a certain process activity. This novel conceptual view is then employed to detect potential data inconsistencies arising when the same data are accessed erroneously by different process activities. The decision perspective encompasses the modeling of the decision-making related to a process, considering where decisions are made in the process and how decision outcomes affect process execution. In this thesis, we investigate the use of the Decision Model and Notation (DMN) standard in conjunction with BPMN starting from a pattern-based approach to ease the derivation of DMN decision models from the data represented in BPMN processes. Besides, we propose a methodology that focuses on the integrated use of BPMN and DMN for modeling decision-intensive care pathways in a real-world application domain
Supporting effective unexpected exception handling in workflow management systems within organizaional contexts
Tese de doutoramento em Informática (Engenharia Informática), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008Workflow Management Systems (WfMS) support the execution of organizational processes within organizations. Processes are modelled using high level languages specifying the sequence of tasks the organization has to perform. However, organizational processes do not have always a smooth flow conforming to any possible designed model and exceptions to the rule happen often. Organizations require flexibility to react to situations not predicted in the model. The required flexibility should be complemented with robustness to guarantee system reliability even in extreme situations. In our work, we have introduced the concept of WfMS resilience that comprises these two facets: robustness and flexibility. The main objective of our work is to increase resilience in WfMSs. From the events demanding for WfMS resilience, we focused on ad hoc effective unexpected exceptions as those for which no previous knowledge exist is the organization to derive the handling procedure and no plan can be a priori established. These exceptions usually require human intervention and problem solving activities, since the concrete situation may not be entirely understood before humans start reacting to the event. After discussing existing approaches to increase WfMS resilience, we have identified five levels of conformity. The fifth level, being the most demanding one, requires unrestricted humanistic interventions to workflow execution. In this thesis, we propose a system to support unrestricted users' interventions to the WfMS and we characterize the interventions as unstructured activities. The system has two modes of operation: it usually works under model control and changes to unstructured activities support when an exception is detected. The exception handling activities are carried out until the system is placed back into a coherent mode, where work may proceed undermodel execution control
Foundations of Multi-Paradigm Modelling for Cyber-Physical Systems
This open access book coherently gathers well-founded information on the fundamentals of and formalisms for modelling cyber-physical systems (CPS). Highlighting the cross-disciplinary nature of CPS modelling, it also serves as a bridge for anyone entering CPS from related areas of computer science or engineering. Truly complex, engineered systems—known as cyber-physical systems—that integrate physical, software, and network aspects are now on the rise. However, there is no unifying theory nor systematic design methods, techniques or tools for these systems. Individual (mechanical, electrical, network or software) engineering disciplines only offer partial solutions. A technique known as Multi-Paradigm Modelling has recently emerged suggesting to model every part and aspect of a system explicitly, at the most appropriate level(s) of abstraction, using the most appropriate modelling formalism(s), and then weaving the results together to form a representation of the system. If properly applied, it enables, among other global aspects, performance analysis, exhaustive simulation, and verification. This book is the first systematic attempt to bring together these formalisms for anyone starting in the field of CPS who seeks solid modelling foundations and a comprehensive introduction to the distinct existing techniques that are multi-paradigmatic. Though chiefly intended for master and post-graduate level students in computer science and engineering, it can also be used as a reference text for practitioners
Integration of Building Information Modeling (BIM) and Process Mining for Design Authoring Processes
Building Information Modelling (BIM) corresponds to the generation and management of the digital representation for building products by wrapping building elements and their information in a unique source file. Open BIM, relying on platform-independent standards, such as IFC (Industry Foundation Classes), is supposed to increase the interoperability in the BIM environment. BIM, as a shared work platform in AEC (Architecture, Engineering and Construction) industry, can be upgraded to act as an Enterprise Resource Management (ERM) system and support data mining for the management of design and construction processes. ERM systems rely on transaction data, also known as “event logs”. eXtensibile Event Stream (XES) is an XML (Extensible Markup Language) schema aiming to provide a format for supporting the interchange of event logs. XES-based Event logs commonly include some semantics (called extensions) regarding events.
This work aims to enable BIM to act as an ERM system. To realize this goal, four research objectives were defined and achieved. First, an ‘IFC archiver algorithm’ was developed to take snapshots, on a regular basis, from different stages of building modeling process (performed in Autodesk Revit), throughout the design phase from start to the end. Second, an ‘IFC logger algorithm’ was created to consecutively compare archived IFC files, detect design activities and save them in the CSV format event log. Then, XESame module is used to map the CSV format event log to the appropriate data format for Process Mining (i.e., XES format event logs). The activities were categorized in five classes: Addition, Removal, Rotation, Relocation of elements (e.g., a wall), and changes in their properties (e.g., the size, type or family of an element). Five attributes for each activity were stored in the database. Those included: Element ID, Designer, Element Name (Name of the Activity), Start and End time of each activity. Third, Process Mining techniques were used to detect the as-happened processes. Last but not least, Process Mining helped to derive different types of design process information (analytics) such as social networks of actors, bottlenecks of processes and process deviations.
Two case studies were performed to validate and verify the research methodology. Around 300 and 30,000 events were captured respectively, during the design phase of our first and second case studies. Then, the activity log was fed to a Process Mining tool to mine the as-happened design processes. Two levels of process maps were discovered: As-happened level 2 and “level 3” BIM maps. As-happened maps were derived and represented in Petri net and process tree formats. Moreover, different types of animations of the as-happened design processes were derived for level 2 and “level 3” BIM maps from replaying the event logs on top of the captured processes. Those animations showed project paths, activities queue lengths and service times.
In a nutshell, the study successfully applied Process Mining on the foundation of BIM (as an ERM system) and accordingly made discovery, monitoring and optimizing BIM processes possible. The present study aims to assist BIM and project managers by enabling BIM as a management tool for design processes. These processes are important, because the design phase is at the early stage of every construction project
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