Tools For Understanding Debugging And Simulation Performance Improvement Of Equation Based Models

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Tools and Methods for Analysis, Debugging, and Performance Improvement of Equation-Based Models

Author : Martin Sjölund
Publisher : Linköping University Electronic Press
ISBN 13 : 9175190710
Total Pages : 243 pages
Book Rating : 4.1/5 (751 download)

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Book Synopsis Tools and Methods for Analysis, Debugging, and Performance Improvement of Equation-Based Models by : Martin Sjölund

Download or read book Tools and Methods for Analysis, Debugging, and Performance Improvement of Equation-Based Models written by Martin Sjölund and published by Linköping University Electronic Press. This book was released on 2015-05-11 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Equation-based object-oriented (EOO) modeling languages such as Modelica provide a convenient, declarative method for describing models of cyber-physical systems. Because of the ease of use of EOO languages, large and complex models can be built with limited effort. However, current state-of-the-art tools do not provide the user with enough information when errors appear or simulation results are wrong. It is of paramount importance that such tools should give the user enough information to correct errors or understand where the problems that lead to wrong simulation results are located. However, understanding the model translation process of an EOO compiler is a daunting task that not only requires knowledge of the numerical algorithms that the tool executes during simulation, but also the complex symbolic transformations being performed. As part of this work, methods have been developed and explored where the EOO tool, an enhanced Modelica compiler, records the transformations during the translation process in order to provide better diagnostics, explanations, and analysis. This information is used to generate better error-messages during translation. It is also used to provide better debugging for a simulation that produces unexpected results or where numerical methods fail. Meeting deadlines is particularly important for real-time applications. It is usually essential to identify possible bottlenecks and either simplify the model or give hints to the compiler that enable it to generate faster code. When profiling and measuring execution times of parts of the model the recorded information can also be used to find out why a particular system model executes slowly. Combined with debugging information, it is possible to find out why this system of equations is slow to solve, which helps understanding what can be done to simplify the model. A tool with a graphical user interface has been developed to make debugging and performance profiling easier. Both debugging and profiling have been combined into a single view so that performance metrics are mapped to equations, which are mapped to debugging information. The algorithmic part of Modelica was extended with meta-modeling constructs (MetaModelica) for language modeling. In this context a quite general approach to debugging and compilation from (extended) Modelica to C code was developed. That makes it possible to use the same executable format for simulation executables as for compiler bootstrapping when the compiler written in MetaModelica compiles itself. Finally, a method and tool prototype suitable for speeding up simulations has been developed. It works by partitioning the model at appropriate places and compiling a simulation executable for a suitable parallel platform.

Methods and Tools for Efficient Model-Based Development of Cyber-Physical Systems with Emphasis on Model and Tool Integration

Author : Alachew Mengist
Publisher : Linköping University Electronic Press
ISBN 13 : 9176850366
Total Pages : 116 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Methods and Tools for Efficient Model-Based Development of Cyber-Physical Systems with Emphasis on Model and Tool Integration by : Alachew Mengist

Download or read book Methods and Tools for Efficient Model-Based Development of Cyber-Physical Systems with Emphasis on Model and Tool Integration written by Alachew Mengist and published by Linköping University Electronic Press. This book was released on 2019-08-21 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Model-based tools and methods are playing important roles in the design and analysis of cyber-physical systems before building and testing physical prototypes. The development of increasingly complex CPSs requires the use of multiple tools for different phases of the development lifecycle, which in turn depends on the ability of the supporting tools to interoperate. However, currently no vendor provides comprehensive end-to-end systems engineering tool support across the entire product lifecycle, and no mature solution currently exists for integrating different system modeling and simulation languages, tools and algorithms in the CPSs design process. Thus, modeling and simulation tools are still used separately in industry. The unique challenges in integration of CPSs are a result of the increasing heterogeneity of components and their interactions, increasing size of systems, and essential design requirements from various stakeholders. The corresponding system development involves several specialists in different domains, often using different modeling languages and tools. In order to address the challenges of CPSs and facilitate design of system architecture and design integration of different models, significant progress needs to be made towards model-based integration of multiple design tools, languages, and algorithms into a single integrated modeling and simulation environment. In this thesis we present the need for methods and tools with the aim of developing techniques for numerically stable co-simulation, advanced simulation model analysis, simulation-based optimization, and traceability capability, and making them more accessible to the model-based cyber physical product development process, leading to more efficient simulation. In particular, the contributions of this thesis are as follows: 1) development of a model-based dynamic optimization approach by integrating optimization into the model development process; 2) development of a graphical co-modeling editor and co-simulation framework for modeling, connecting, and unified system simulation of several different modeling tools using the TLM technique; 3) development of a tool-supported method for multidisciplinary collaborative modeling and traceability support throughout the development process for CPSs; 4) development of an advanced simulation modeling analysis tool for more efficient simulation.

Extensions for Distributed Moving Base Driving Simulators

Author : Anders Andersson
Publisher : Linköping University Electronic Press
ISBN 13 : 9176855244
Total Pages : 39 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Extensions for Distributed Moving Base Driving Simulators by : Anders Andersson

Download or read book Extensions for Distributed Moving Base Driving Simulators written by Anders Andersson and published by Linköping University Electronic Press. This book was released on 2017-03-30 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern vehicles are complex systems. Different design stages for such a complex system include evaluation using models and submodels, hardware-in-the-loop systems and complete vehicles. Once a vehicle is delivered to the market evaluation continues by the public. One kind of tool that can be used during many stages of a vehicle lifecycle is driving simulators. The use of driving simulators with a human driver is commonly focused on driver behavior. In a high fidelity moving base driving simulator it is possible to provide realistic and repetitive driving situations using distinctive features such as: physical modelling of driven vehicle, a moving base, a physical cabin interface and an audio and visual representation of the driving environment. A desired but difficult goal to achieve using a moving base driving simulator is to have behavioral validity. In other words, A driver in a moving base driving simulator should have the same driving behavior as he or she would have during the same driving task in a real vehicle.". In this thesis the focus is on high fidelity moving base driving simulators. The main target is to improve the behavior validity or to maintain behavior validity while adding complexity to the simulator. One main assumption in this thesis is that systems closer to the final product provide better accuracy and are perceived better if properly integrated. Thus, the approach in this thesis is to try to ease incorporation of such systems using combinations of the methods hardware-in-the-loop and distributed simulation. Hardware-in-the-loop is a method where hardware is interfaced into a software controlled environment/simulation. Distributed simulation is a method where parts of a simulation at physically different locations are connected together. For some simulator laboratories distributed simulation is the only feasible option since some hardware cannot be moved in an easy way. Results presented in this thesis show that a complete vehicle or hardware-in-the-loop test laboratory can successfully be connected to a moving base driving simulator. Further, it is demonstrated that using a framework for distributed simulation eases communication and integration due to standardized interfaces. One identified potential problem is complexity in interface wrappers when integrating hardware-in-the-loop in a distributed simulation framework. From this aspect, it is important to consider the model design and the intersections between software and hardware models. Another important issue discussed is the increased delay in overhead time when using a framework for distributed simulation.

Designing a Modern Skeleton Programming Framework for Parallel and Heterogeneous Systems

Author : August Ernstsson
Publisher : Linköping University Electronic Press
ISBN 13 : 9179297722
Total Pages : 155 pages
Book Rating : 4.1/5 (792 download)

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Book Synopsis Designing a Modern Skeleton Programming Framework for Parallel and Heterogeneous Systems by : August Ernstsson

Download or read book Designing a Modern Skeleton Programming Framework for Parallel and Heterogeneous Systems written by August Ernstsson and published by Linköping University Electronic Press. This book was released on 2020-10-21 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today's society is increasingly software-driven and dependent on powerful computer technology. Therefore it is important that advancements in the low-level processor hardware are made available for exploitation by a growing number of programmers of differing skill level. However, as we are approaching the end of Moore's law, hardware designers are finding new and increasingly complex ways to increase the accessible processor performance. It is getting more and more difficult to effectively target these processing resources without expert knowledge in parallelization, heterogeneous computation, communication, synchronization, and so on. To ensure that the software side can keep up, advanced programming environments and frameworks are needed to bridge the widening gap between hardware and software. One such example is the pattern-centric skeleton programming model and in particular the SkePU project. The work presented in this thesis first redesigns the SkePU framework based on modern C++ variadic template metaprogramming and state-of-the-art compiler technology. It then explores new ways to improve performance: by providing new patterns, improving the data access locality of existing ones, and using both static and dynamic knowledge about program flow. The work combines novel ideas with practical evaluation of the approach on several applications. The advancements also include the first skeleton API that allows variadic skeletons, new data containers, and finally an approach to make skeleton programming more customizable without compromising universal portability.

Exploring C2 Capability and Effectiveness in Challenging Situations

Author : Magdalena Granåsen
Publisher : Linköping University Electronic Press
ISBN 13 : 917685082X
Total Pages : 66 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Exploring C2 Capability and Effectiveness in Challenging Situations by : Magdalena Granåsen

Download or read book Exploring C2 Capability and Effectiveness in Challenging Situations written by Magdalena Granåsen and published by Linköping University Electronic Press. This book was released on 2019-05-27 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern societies are affected by various threats and hazards, including natural disasters, cyber-attacks, extreme weather events and inter-state conflicts. Managing these challenging situations requires immediate actions, suspension of ordinary procedures, decision making under uncertainty and coordinated action. In other words, challenging situations put high demands on the command and control (C2) capability. To strengthen the capability of C2, it is vital to identify the prerequisites for effective coordination and direction within the domain of interest. This thesis explores C2 capability and effectiveness in three domains: interorganizational crisis management, military command and control, and cyber defence operations. The thesis aims to answer three research questions: (1) What constitutes C2 capability? (2) What constitutes C2 effectiveness? and (3) How can C2 effectiveness be assessed? The work was carried out as two case studies and one systematic literature review. The main contributions of the thesis are the identification of perspectives of C2 capability in challenging situations and an overview of approaches to C2 effectiveness assessment. Based on the results of the three studies, six recurring perspectives of capability in the domains studied were identified: interaction (collaboration), direction and coordination, relationships, situation awareness, resilience and preparedness. In the domains there are differences concerning which perspectives that are most emphasized in order obtain C2 capability. C2 effectiveness is defined as the extent to which a C2 system is successful in achieving its intended result. The thesis discusses the interconnectedness of performance and effectiveness measures, and concludes that there is not a united view on the difference between measures of effectiveness and measures of performance. Different approaches to effectiveness assessment were identified, where assessment may be conducted based on one specific issue, in relation to a defined goal for a C2 function or using a more exploratory approach.

Spatio-Temporal Stream Reasoning with Adaptive State Stream Generation

Author : Daniel de Leng
Publisher : Linköping University Electronic Press
ISBN 13 : 9176854760
Total Pages : 153 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Spatio-Temporal Stream Reasoning with Adaptive State Stream Generation by : Daniel de Leng

Download or read book Spatio-Temporal Stream Reasoning with Adaptive State Stream Generation written by Daniel de Leng and published by Linköping University Electronic Press. This book was released on 2017-09-08 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: A lot of today's data is generated incrementally over time by a large variety of producers. This data ranges from quantitative sensor observations produced by robot systems to complex unstructured human-generated texts on social media. With data being so abundant, making sense of these streams of data through reasoning is challenging. Reasoning over streams is particularly relevant for autonomous robotic systems that operate in a physical environment. They commonly observe this environment through incremental observations, gradually refining information about their surroundings. This makes robust management of streaming data and its refinement an important problem. Many contemporary approaches to stream reasoning focus on the issue of querying data streams in order to generate higher-level information by relying on well-known database approaches. Other approaches apply logic-based reasoning techniques, which rarely consider the provenance of their symbolic interpretations. In this thesis, we integrate techniques for logic-based spatio-temporal stream reasoning with the adaptive generation of the state streams needed to do the reasoning over. This combination deals with both the challenge of reasoning over streaming data and the problem of robustly managing streaming data and its refinement. The main contributions of this thesis are (1) a logic-based spatio-temporal reasoning technique that combines temporal reasoning with qualitative spatial reasoning; (2) an adaptive reconfiguration procedure for generating and maintaining a data stream required to perform spatio-temporal stream reasoning over; and (3) integration of these two techniques into a stream reasoning framework. The proposed spatio-temporal stream reasoning technique is able to reason with intertemporal spatial relations by leveraging landmarks. Adaptive state stream generation allows the framework to adapt in situations in which the set of available streaming resources changes. Management of streaming resources is formalised in the DyKnow model, which introduces a configuration life-cycle to adaptively generate state streams. The DyKnow-ROS stream reasoning framework is a concrete realisation of this model that extends the Robot Operating System (ROS). DyKnow-ROS has been deployed on the SoftBank Robotics NAO platform to demonstrate the system's capabilities in the context of a case study on run-time adaptive reconfiguration. The results show that the proposed system – by combining reasoning over and reasoning about streams – can robustly perform spatio-temporal stream reasoning, even when the availability of streaming resources changes.

Automatic Verification of Parameterized Systems by Over-Approximation

Author : Vladislavs Jahundovics
Publisher : Linköping University Electronic Press
ISBN 13 : 9176859185
Total Pages : 155 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Automatic Verification of Parameterized Systems by Over-Approximation by : Vladislavs Jahundovics

Download or read book Automatic Verification of Parameterized Systems by Over-Approximation written by Vladislavs Jahundovics and published by Linköping University Electronic Press. This book was released on 2015-11-17 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a completely automatic verification framework to check safety properties of parameterized systems. A parameterized system is a family of finite state systems where every system consists of a finite number of processes running in parallel the same algorithm. All the systems in the family differ only in the number of the processes and, in general, the number of systems in a family may be unbounded. Examples of parameterized systems are communication protocols, mutual exclusion protocols, cache coherence protocols, distributed algorithms etc. Model-checking of finite state systems is a well-developed formal verification approach of proving properties of systems in an automatic way. However, it cannot be applied directly to parameterized systems because the unbounded number of systems in a family means an infinite state space. In this thesis we propose to abstract an original family of systems consisting of an unbounded number of processes into one consisting of a fixed number of processes. An abstracted system is considered to consist of k+1 components—k reference processes and their environment. The transition relation for the abstracted system is an over-approximation of the transition relation for the original system, therefore, a set of reachable states of the abstracted system is an over-approximation of the set of reachable states of the original one. A safety property is considered to be parameterized by a fixed number of processes whose relationship is in the center of attention in the property. Such processes serve as reference processes in the abstraction. We propose an encoding which allows to perform reachability analysis for an abstraction parameterized by the reference processes. We have successfully verified three classic parameterized systems with replicated processes by applying this method.

Latency-aware Resource Management at the Edge

Author : Klervie Toczé
Publisher : Linköping University Electronic Press
ISBN 13 : 9179299040
Total Pages : 148 pages
Book Rating : 4.1/5 (792 download)

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Book Synopsis Latency-aware Resource Management at the Edge by : Klervie Toczé

Download or read book Latency-aware Resource Management at the Edge written by Klervie Toczé and published by Linköping University Electronic Press. This book was released on 2020-02-19 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: The increasing diversity of connected devices leads to new application domains being envisioned. Some of these need ultra low latency or have privacy requirements that cannot be satisfied by the current cloud. By bringing resources closer to the end user, the recent edge computing paradigm aims to enable such applications. One critical aspect to ensure the successful deployment of the edge computing paradigm is efficient resource management. Indeed, obtaining the needed resources is crucial for the applications using the edge, but the resource picture of this paradigm is complex. First, as opposed to the nearly infinite resources provided by the cloud, the edge devices have finite resources. Moreover, different resource types are required depending on the applications and the devices supplying those resources are very heterogeneous. This thesis studies several challenges towards enabling efficient resource management for edge computing. The thesis begins by a review of the state-of-the-art research focusing on resource management in the edge computing context. A taxonomy is proposed for providing an overview of the current research and identify areas in need of further work. One of the identified challenges is studying the resource supply organization in the case where a mix of mobile and stationary devices is used to provide the edge resources. The ORCH framework is proposed as a means to orchestrate this edge device mix. The evaluation performed in a simulator shows that this combination of devices enables higher quality of service for latency-critical tasks. Another area is understanding the resource demand side. The thesis presents a study of the workload of a killer application for edge computing: mixed reality. The MR-Leo prototype is designed and used as a vehicle to understand the end-to-end latency, the throughput, and the characteristics of the workload for this type of application. A method for modeling the workload of an application is devised and applied to MR-Leo in order to obtain a synthetic workload exhibiting the same characteristics, which can be used in further studies.

Towards Semantically Enabled Complex Event Processing

Author : Robin Keskisärkkä
Publisher : Linköping University Electronic Press
ISBN 13 : 9176854795
Total Pages : 169 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Towards Semantically Enabled Complex Event Processing by : Robin Keskisärkkä

Download or read book Towards Semantically Enabled Complex Event Processing written by Robin Keskisärkkä and published by Linköping University Electronic Press. This book was released on 2017-10-30 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Semantic Web provides a framework for semantically annotating data on the web, and the Resource Description Framework (RDF) supports the integration of structured data represented in heterogeneous formats. Traditionally, the Semantic Web has focused primarily on more or less static data, but information on the web today is becoming increasingly dynamic. RDF Stream Processing (RSP) systems address this issue by adding support for streaming data and continuous query processing. To some extent, RSP systems can be used to perform complex event processing (CEP), where meaningful high-level events are generated based on low-level events from multiple sources; however, there are several challenges with respect to using RSP in this context. Event models designed to represent static event information lack several features required for CEP, and are typically not well suited for stream reasoning. The dynamic nature of streaming data also greatly complicates the development and validation of RSP queries. Therefore, reusing queries that have been prepared ahead of time is important to be able to support real-time decision-making. Additionally, there are limitations in existing RSP implementations in terms of both scalability and expressiveness, where some features required in CEP are not supported by any of the current systems. The goal of this thesis work has been to address some of these challenges and the main contributions of the thesis are: (1) an event model ontology targeted at supporting CEP; (2) a model for representing parameterized RSP queries as reusable templates; and (3) an architecture that allows RSP systems to be integrated for use in CEP. The proposed event model tackles issues specifically related to event modeling in CEP that have not been sufficiently covered by other event models, includes support for event encapsulation and event payloads, and can easily be extended to fit specific use-cases. The model for representing RSP query templates was designed as an extension to SPIN, a vocabulary that supports modeling of SPARQL queries as RDF. The extended model supports the current version of the RSP Query Language (RSP-QL) developed by the RDF Stream Processing Community Group, along with some of the most popular RSP query languages. Finally, the proposed architecture views RSP queries as individual event processing agents in a more general CEP framework. Additional event processing components can be integrated to provide support for operations that are not supported in RSP, or to provide more efficient processing for specific tasks. We demonstrate the architecture in implementations for scenarios related to traffic-incident monitoring, criminal-activity monitoring, and electronic healthcare monitoring.

Web Authentication using Third-Parties in Untrusted Environments

Author : Anna Vapen
Publisher : Linköping University Electronic Press
ISBN 13 : 9176857530
Total Pages : 91 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Web Authentication using Third-Parties in Untrusted Environments by : Anna Vapen

Download or read book Web Authentication using Third-Parties in Untrusted Environments written by Anna Vapen and published by Linköping University Electronic Press. This book was released on 2016-08-22 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the increasing personalization of the Web, many websites allow users to create their own personal accounts. This has resulted in Web users often having many accounts on different websites, to which they need to authenticate in order to gain access. Unfortunately, there are several security problems connected to the use and re-use of passwords, the most prevalent authentication method currently in use, including eavesdropping and replay attacks. Several alternative methods have been proposed to address these shortcomings, including the use of hardware authentication devices. However, these more secure authentication methods are often not adapted for mobile Web users who use different devices in different places and in untrusted environments, such as public Wi-Fi networks, to access their accounts. We have designed a method for comparing, evaluating and designing authentication solutions suitable for mobile users and untrusted environments. Our method leverages the fact that mobile users often bring their own cell phones, and also takes into account different levels of security adapted for different services on the Web. Another important trend in the authentication landscape is that an increasing number of websites use third-party authentication. This is a solution where users have an account on a single system, the identity provider, and this one account can then be used with multiple other websites. In addition to requiring fewer passwords, these services can also in some cases implement authentication with higher security than passwords can provide. How websites select their third-party identity providers has privacy and security implications for end users. To better understand the security and privacy risks with these services, we present a data collection methodology that we have used to identify and capture third-party authentication usage on the Web. We have also characterized the third-party authentication landscape based on our collected data, outlining which types of third-parties are used by which types of sites, and how usage differs across the world. Using a combination of large-scale crawling, longitudinal manual testing, and in-depth login tests, our characterization and analysis has also allowed us to discover interesting structural properties of the landscape, differences in the cross-site relationships, and how the use of third-party authentication is changing over time. Finally, we have also outlined what information is shared between websites in third-party authentication, dened risk classes based on shared data, and proled privacy leakage risks associated with websites and their identity providers sharing data with each other. Our ndings show how websites can strengthen the privacy of their users based on how these websites select and combine their third-parties and the data they allow to be shared.

Computational Complexity of some Optimization Problems in Planning

Author : Meysam Aghighi
Publisher : Linköping University Electronic Press
ISBN 13 : 9176855198
Total Pages : 59 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Computational Complexity of some Optimization Problems in Planning by : Meysam Aghighi

Download or read book Computational Complexity of some Optimization Problems in Planning written by Meysam Aghighi and published by Linköping University Electronic Press. This book was released on 2017-05-17 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: Automated planning is known to be computationally hard in the general case. Propositional planning is PSPACE-complete and first-order planning is undecidable. One method for analyzing the computational complexity of planning is to study restricted subsets of planning instances, with the aim of differentiating instances with varying complexity. We use this methodology for studying the computational complexity of planning. Finding new tractable (i.e. polynomial-time solvable) problems has been a particularly important goal for researchers in the area. The reason behind this is not only to differentiate between easy and hard planning instances, but also to use polynomial-time solvable instances in order to construct better heuristic functions and improve planners. We identify a new class of tractable cost-optimal planning instances by restricting the causal graph. We study the computational complexity of oversubscription planning (such as the net-benefit problem) under various restrictions and reveal strong connections with classical planning. Inspired by this, we present a method for compiling oversubscription planning problems into the ordinary plan existence problem. We further study the parameterized complexity of cost-optimal and net-benefit planning under the same restrictions and show that the choice of numeric domain for the action costs has a great impact on the parameterized complexity. We finally consider the parameterized complexity of certain problems related to partial-order planning. In some applications, less restricted plans than total-order plans are needed. Therefore, a partial-order plan is being used instead. When dealing with partial-order plans, one important question is how to achieve optimal partial order plans, i.e. having the highest degree of freedom according to some notion of flexibility. We study several optimization problems for partial-order plans, such as finding a minimum deordering or reordering, and finding the minimum parallel execution length.

Formal Verification of Tree Ensembles in Safety-Critical Applications

Author : John Törnblom
Publisher : Linköping University Electronic Press
ISBN 13 : 917929748X
Total Pages : 22 pages
Book Rating : 4.1/5 (792 download)

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Book Synopsis Formal Verification of Tree Ensembles in Safety-Critical Applications by : John Törnblom

Download or read book Formal Verification of Tree Ensembles in Safety-Critical Applications written by John Törnblom and published by Linköping University Electronic Press. This book was released on 2020-10-28 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the presence of data and computational resources, machine learning can be used to synthesize software automatically. For example, machines are now capable of learning complicated pattern recognition tasks and sophisticated decision policies, two key capabilities in autonomous cyber-physical systems. Unfortunately, humans find software synthesized by machine learning algorithms difficult to interpret, which currently limits their use in safety-critical applications such as medical diagnosis and avionic systems. In particular, successful deployments of safety-critical systems mandate the execution of rigorous verification activities, which often rely on human insights, e.g., to identify scenarios in which the system shall be tested. A natural pathway towards a viable verification strategy for such systems is to leverage formal verification techniques, which, in the presence of a formal specification, can provide definitive guarantees with little human intervention. However, formal verification suffers from scalability issues with respect to system complexity. In this thesis, we investigate the limits of current formal verification techniques when applied to a class of machine learning models called tree ensembles, and identify model-specific characteristics that can be exploited to improve the performance of verification algorithms when applied specifically to tree ensembles. To this end, we develop two formal verification techniques specifically for tree ensembles, one fast and conservative technique, and one exact but more computationally demanding. We then combine these two techniques into an abstraction-refinement approach, that we implement in a tool called VoTE (Verifier of Tree Ensembles). Using a couple of case studies, we recognize that sets of inputs that lead to the same system behavior can be captured precisely as hyperrectangles, which enables tractable enumeration of input-output mappings when the input dimension is low. Tree ensembles with a high-dimensional input domain, however, seems generally difficult to verify. In some cases though, conservative approximations of input-output mappings can greatly improve performance. This is demonstrated in a digit recognition case study, where we assess the robustness of classifiers when confronted with additive noise.

Gated Bayesian Networks

Author : Marcus Bendtsen
Publisher : Linköping University Electronic Press
ISBN 13 : 9176855252
Total Pages : 245 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Gated Bayesian Networks by : Marcus Bendtsen

Download or read book Gated Bayesian Networks written by Marcus Bendtsen and published by Linköping University Electronic Press. This book was released on 2017-06-08 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bayesian networks have grown to become a dominant type of model within the domain of probabilistic graphical models. Not only do they empower users with a graphical means for describing the relationships among random variables, but they also allow for (potentially) fewer parameters to estimate, and enable more efficient inference. The random variables and the relationships among them decide the structure of the directed acyclic graph that represents the Bayesian network. It is the stasis over time of these two components that we question in this thesis. By introducing a new type of probabilistic graphical model, which we call gated Bayesian networks, we allow for the variables that we include in our model, and the relationships among them, to change overtime. We introduce algorithms that can learn gated Bayesian networks that use different variables at different times, required due to the process which we are modelling going through distinct phases. We evaluate the efficacy of these algorithms within the domain of algorithmic trading, showing how the learnt gated Bayesian networks can improve upon a passive approach to trading. We also introduce algorithms that detect changes in the relationships among the random variables, allowing us to create a model that consists of several Bayesian networks, thereby revealing changes and the structure by which these changes occur. The resulting models can be used to detect the currently most appropriate Bayesian network, and we show their use in real-world examples from both the domain of sports analytics and finance.

Completion of Ontologies and Ontology Networks

Author : Zlatan Dragisic
Publisher : Linköping University Electronic Press
ISBN 13 : 9176855228
Total Pages : 88 pages
Book Rating : 4.1/5 (768 download)

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Book Synopsis Completion of Ontologies and Ontology Networks by : Zlatan Dragisic

Download or read book Completion of Ontologies and Ontology Networks written by Zlatan Dragisic and published by Linköping University Electronic Press. This book was released on 2017-08-22 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: The World Wide Web contains large amounts of data, and in most cases this data has no explicit structure. The lack of structure makes it difficult for automated agents to understand and use such data. A step towards a more structured World Wide Web is the Semantic Web, which aims at introducing semantics to data on the World Wide Web. One of the key technologies in this endeavour are ontologies, which provide a means for modeling a domain of interest and are used for search and integration of data. In recent years many ontologies have been developed. To be able to use multiple ontologies it is necessary to align them, i.e., find inter-ontology relationships. However, developing and aligning ontologies is not an easy task and it is often the case that ontologies and their alignments are incorrect and incomplete. This can be a problem for semantically-enabled applications. Incorrect and incomplete ontologies and alignments directly influence the quality of the results of such applications, as wrong results can be returned and correct results can be missed. This thesis focuses on the problem of completing ontologies and ontology networks. The contributions of the thesis are threefold. First, we address the issue of completing the is-a structure and alignment in ontologies and ontology networks. We have formalized the problem of completing the is-a structure in ontologies as an abductive reasoning problem and developed algorithms as well as systems for dealing with the problem. With respect to the completion of alignments, we have studied system performance in the Ontology Alignment Evaluation Initiative, a yearly evaluation campaign for ontology alignment systems. We have also addressed the scalability of ontology matching, which is one of the current challenges, by developing an approach for reducing the search space when generating the alignment.Second, high quality completion requires user involvement. As users' time and effort are a limited resource we address the issue of limiting and facilitating user interaction in the completion process. We have conducted a broad study of state-of-the-art ontology alignment systems and identified different issues related to the process. We have also conducted experiments to assess the impact of user errors in the completion process. While the completion of ontologies and ontology networks can be done at any point in the life-cycle of ontologies and ontology networks, some of the issues can be addressed already in the development phase. The third contribution of the thesis addresses this by introducing ontology completion and ontology alignment into an existing ontology development methodology.

Principles of Object-Oriented Modeling and Simulation with Modelica 3.3

Author : Peter Fritzson
Publisher : John Wiley & Sons
ISBN 13 : 1118859162
Total Pages : 1268 pages
Book Rating : 4.1/5 (188 download)

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Book Synopsis Principles of Object-Oriented Modeling and Simulation with Modelica 3.3 by : Peter Fritzson

Download or read book Principles of Object-Oriented Modeling and Simulation with Modelica 3.3 written by Peter Fritzson and published by John Wiley & Sons. This book was released on 2015-01-06 with total page 1268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fritzson covers the Modelica language in impressive depth from the basic concepts such as cyber-physical, equation-base, object-oriented, system, model, and simulation, while also incorporating over a hundred exercises and their solutions for a tutorial, easy-to-read experience. The only book with complete Modelica 3.3 coverage Over one hundred exercises and solutions Examines basic concepts such as cyber-physical, equation-based, object-oriented, system, model, and simulation

Principles of Object-Oriented Modeling and Simulation with Modelica 2.1

Author : Peter Fritzson
Publisher : John Wiley & Sons
ISBN 13 : 0470937610
Total Pages : 944 pages
Book Rating : 4.4/5 (79 download)

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Book Synopsis Principles of Object-Oriented Modeling and Simulation with Modelica 2.1 by : Peter Fritzson

Download or read book Principles of Object-Oriented Modeling and Simulation with Modelica 2.1 written by Peter Fritzson and published by John Wiley & Sons. This book was released on 2010-08-31 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides an introduction to modern object-oriented design principles and applications for the fast-growing area of modeling and simulation Covers the topic of multi-domain system modeling and design with applications that have components from several areas Serves as a reference for the Modelica language as well as a comprehensive overview of application model libraries for a number of application domains

Simulation, Modeling, and Programming for Autonomous Robots

Author : Noriako Ando
Publisher : Springer
ISBN 13 : 3642173195
Total Pages : 572 pages
Book Rating : 4.6/5 (421 download)

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Book Synopsis Simulation, Modeling, and Programming for Autonomous Robots by : Noriako Ando

Download or read book Simulation, Modeling, and Programming for Autonomous Robots written by Noriako Ando and published by Springer. This book was released on 2010-11-11 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: Why are the many highly capable autonomous robots that have been promised for novel applications driven by society, industry, and research not available - day despite the tremendous progress in robotics science and systems achieved during the last decades? Unfortunately, steady improvements in speci?c robot abilities and robot hardware have not been matched by corresponding robot performance in real world environments. This is mainly due to the lack of - vancements in robot software that master the development of robotic systems of ever increasing complexity. In addition, fundamental open problems are still awaiting sound answers while the development of new robotics applications s- fersfromthelackofwidelyusedtools,libraries,andalgorithmsthataredesigned in a modular and performant manner with standardized interfaces. Simulation environments are playing a major role not only in reducing development time and cost, e. g. , by systematic software- or hardware-in-the-loop testing of robot performance, but also in exploring new types of robots and applications. H- ever,their use may still be regardedwith skepticism. Seamless migrationof code using robot simulators to real-world systems is still a rare circumstance, due to the complexity of robot, world, sensor, and actuator modeling. These challenges drive the quest for the next generation of methodologies and tools for robot development. The objective of the International Conference on Simulation, Modeling, and ProgrammingforAutonomous Robots (SIMPAR) is to o?er a unique forum for these topics and to bring together researchersfrom academia and industry to identify and solve the key issues necessary to ease the development of increasingly complex robot software.