Modern real-time applications are very dynamic and cannot cope with the use of worst case execution time to avoid overload situations. Therefore scheduling algorithms that are able to prevent timing faults during over...
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ISBN:
(纸本)9780769527659
Modern real-time applications are very dynamic and cannot cope with the use of worst case execution time to avoid overload situations. Therefore scheduling algorithms that are able to prevent timing faults during overload are required. In this context, the value parameter has become useful to add generality and flexibility to such systems. In this paper we present the scheduling algorithm called DMB (Dynamic Misses Based), which is capable of dynamically changing tasks value in order to adjust their importance according to its timing faults rate. The main goal of DMB is to allow the prediction of timing faults during overloads and thereby support a dynamic tuning of tasks fault rate. It is used to enhance the features of the previously defined TAFT (time-Aware Fault-Tolerant) scheduler Obtained results show that DMB in conjunction with TAFT reached the most promising results during overloads, allowing to control tasks degradation in a graceful and determined way.
Many emerging applications operate on continuous unbounded data streams and need real-time data services. Providing deadline guarantees for queries over dynamic data streams is a challenging problem due to bursty stre...
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ISBN:
(纸本)9780769527659
Many emerging applications operate on continuous unbounded data streams and need real-time data services. Providing deadline guarantees for queries over dynamic data streams is a challenging problem due to bursty stream rates and time-varying contents. This paper presents a prediction-based QoS management scheme for real-time data stream query processing in distributed environments. The prediction-based QoS management scheme features query workload estimators, which predict the query workload using execution time profiling and input data sampling. In this paper, we apply the prediction-based technique to select the proper propagation schemes for data streams and intermediate query results in distributed environments. The performance study demonstrates that the proposed solution tolerates dramatic workload fluctuations and saves significant amounts of CPU time and network bandwidth with little overhead.
Requirements of High Integrity systems now encompass distribution mechanisms along with strong functional and non-functional features (run-time support for hardware, dependability, safety, analyzability). In this pape...
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ISBN:
(纸本)9780769527659
Requirements of High Integrity systems now encompass distribution mechanisms along with strong functional and non-functional features (run-time support for hardware, dependability, safety, analyzability). In this paper, we show how model processing help addressing such needs. We present a generic distribution model suitable for High Integrity systems, and demonstrate how a high-level modeling deployment view allows one to greatly reduce the model complexity. Finally, we conclude by assessing a case study.
This work presents a proposal to use aspect orientation in the analysis and design of distributed Embedded real-time Systems (DERTS). These systems have several requirements directly related to their main characterist...
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ISBN:
(纸本)9780769527659
This work presents a proposal to use aspect orientation in the analysis and design of distributed Embedded real-time Systems (DERTS). These systems have several requirements directly related to their main characteristics, the so-called Non-Functional Requirements (NFR), which refer to orthogonal properties, conditions, and restrictions that are spread out over the entire system. Pure object-oriented methods do not address successfully those so called crosscutting concerns, so new technologies, like aspect orientation, are applied in order to fulfill this gap. The paper presents DERAF - distributed Embedded real-time Aspects Framework, an extensible and high-level framework (i.e. implementation-independent) to handle NFR of DERTS at earlier design stages. DERAF combines the use of aspects with RT-UML, aiming to separate the handling of non-functional from functional requirements in the Model Driven Design of DERTS. The paper presents the use of DERAF on a case study of an unmanned air vehicle (UAV).
Nowadays, there are many protocols able to cope with process crashes, but, unfortunately, a process crash represents only a particular faulty behavior. Handling tougher failures (e.g. sending omission failures, receiv...
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ISBN:
(纸本)9780769527659
Nowadays, there are many protocols able to cope with process crashes, but, unfortunately, a process crash represents only a particular faulty behavior. Handling tougher failures (e.g. sending omission failures, receive omission failures, arbitrary failures) is a real practical challenge due to malicious attacks or unexpected software errors. This paper proposes a component-based methodology allowing to take a protocol A resilient to crash failures and to add software components, namely liveness and safety failure detectors, in order to adapt the protocol A to be resilient to more general failures than crashes, without changing the code of A.. Then, the feasibility of this approach is shown, by providing an implementation of liveness failure detectors and of safer failure detectors for a protocol solving the problem of global data computation.
Sensor networks introduce a new application domain and set of challenges in distributedcomputing including new network-level programming languages, global system abstractions, and general-purpose communication protoc...
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ISBN:
(纸本)9780769527659
Sensor networks introduce a new application domain and set of challenges in distributedcomputing including new network-level programming languages, global system abstractions, and general-purpose communication protocols. These challenges are brought about by the tight integration of computation, communication, and distributedreal-time interaction with the physical world. With the growing interest in interconnecting different sensor networks across a wide-area communication infrastructure, an overarching challenge becomes one of arriving at an agreed-upon global sensor network architecture that ensures interoperability. Unlike the Internet, where a layered communication stack (namely, the TCP/IP stack) defines the network architecture, a sensor network architecture must unify not only communication interfaces but also programming interfaces, sit-ice network communication and computation functions are tightly intertwined. In that sense, the sensor network architecture refers to a layered stack of distributedcomputing abstractions. This paper presents an architecture and key considerations in designing and interconnecting local and global sensor networks. Candidate protocols and middleware instantiations are described from the authors' ongoing work that meet the discussed considerations.
We consider the problem of recovering from failures of distributable threads in distributedreal-time systems that operate tinder run-time uncertainties including those on thread execution times, thread arrivals, and ...
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ISBN:
(纸本)9780769527659
We consider the problem of recovering from failures of distributable threads in distributedreal-time systems that operate tinder run-time uncertainties including those on thread execution times, thread arrivals, and node failure occurrences. When a thread encounters a node failure, it causes orphans. Under a termination model, the orphans must be detected and aborted, and exceptions must be delivered to farthest, contiguous surviving thread segment for resuming thread execution. Our application/scheduling model includes distributable threads and their exception handlers that are subject to time/utility function (TUF) time constraints and an utility accrual (UA) optimality criterion. A key underpinning of the TUF/UA scheduling paradigm is the notion of "best-effort" where high importance threads are always favored over low importance ones, irrespective of thread urgency. We present a scheduling algorithm called HUA and a thread integrity protocol called TPR. We show that HUA and TPR bound the orphan cleanup and recovery time with bounded loss of the best-effort property. Our implementation experience of HUA/TPR within Sun's distributedreal-time Specification for Java demonstrates the algorithm/protocol's effectiveness.
During the last years, component based software development has become a well accepted software engineering paradigm within the automotive industry. This fact is not only reflected by upcoming development tools but al...
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ISBN:
(纸本)9780769527659
During the last years, component based software development has become a well accepted software engineering paradigm within the automotive industry. This fact is not only reflected by upcoming development tools but also by newly arising automotive software standards. In component based software engineering, applications are built by assembling small reusable building blocks, the components. Typically more than one component implementation meets the application developer's requirements, so proper selection of the assembled components becomes a key element of the whole procurement and engineering process. This paper's contribution is twofold: First, a basic set of performance and dependability metrics and measures for automotive components is identified. Second, a unified benchmarking process is proposed, that allows an unambiguous comparison of distinct component implementations of a given component class.
While electing an eventual common leader despite process crashes, in a shared memory system where the processes communicate only by reading and writing shared registers is possible when the processes progress synchron...
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ISBN:
(纸本)9780769527659
While electing an eventual common leader despite process crashes, in a shared memory system where the processes communicate only by reading and writing shared registers is possible when the processes progress synchronously, this problem becomes impossible to solve as soon as the processes can progress in a fully asynchronous way. So, an important problem consists in finding additional behavioral assumptions that are, at the same time "as weak as possible" (in order they are practically always satisfied), and "strong enough" in order to allow implementing an eventual leader service despite the net effect of asynchrony and failures. This paper focuses on this dilemma. Afore explicitly, it investigates a timing assumption that allows implementing an eventual leader in presence of partial asynchrony and process crashes. The proposed timing assumptions are particularly weak. They are the following: after some time (i) there is a process that behaves synchronously, and (ii) (t - f) other processes have timers that work correctly (t is the maximal number of processes that may crash, and f the actual number of process crashes;a tinier works incorrectly when it expires too early with respect to the value it has been set). Then, the paper proposes a t-resilient protocol that elects an eventual common leader in any shared memory system that satisfies the previous assumption. Interestingly, this protocol is based on simple design principles.
The design and implementation of distributed High Performance computing (HPC) applications is becoming harder as the scale and number of distributed resources and application is growing. Programming abstractions, libr...
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ISBN:
(纸本)9780769529226
The design and implementation of distributed High Performance computing (HPC) applications is becoming harder as the scale and number of distributed resources and application is growing. Programming abstractions, libraries and frameworks are needed to better overcome that complexity. Moreover when Quality of service (QoS) requirements such as load balancing, efficient resource usage and fault tolerance have to be met, the resulting code is harder to develop, maintain, and reuse, as the code for providing the QoS requirements gets normally mixed with the functionality code. component Technology, on the other hand, allows a better modularity and reusability of applications and even a better support for the development of distributed applications, as those applications can be partitioned in terms of components installed and running (deployed) in the different hosts participating in the system. components also have requirements in forms of the aforementioned non-junctional aspects. In our approach, the code for ensuring these aspects can be automatically generated based on the requirements stated by components and applications, thus leveraging the component implementer of having to deal with these non-functional aspects. In this paper we present the characteristics and the convenience of the generated code for dealing with load balancing, distribution, and fault-tolerance aspects in the context of CORBA-LC. CORBA-LC is a lightweight distributed reflective component model based on CORBA that imposes a peer network model in which the whole network acts as a repository for managing and assigning the whole set of resources: components, CPU cycles, memory, etc.
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