24862782
A Robust Load Balancing Pattern for Grid Computing
Availability of grid resources is dynamic, which raises the need to develop robust and effective applications against changing circumstances. The paper proposes a robust load balancing pattern and centralized control task scheduler is discussed. Based on improving fault tolerant service on request chain processing, the paper enhances ORBUS1.1 software with load balancing service. Simulation results show that the implementation is able to obtain high system performance with central-control task scheduling and MAXPERFORMpolicy.
27110930
Solving the Group Priority Inversion Problem in a Timed Asynchronous System
Considers the priority inversion problem in an actively replicated system. Priority inversion was originally defined in the context of nonreplicated systems. Therefore, we first introduce the concept of group priority inversion, which extends the concept of (local) priority inversion to the context of a group of processors that perform an actively replicated processing. We then present the properties of a request scheduling protocol to enforce a total ordering for the processing of requests while avoiding group priority inversions. These properties have been implemented in a protocol that relies on a timed asynchronous system model equipped with a failure detector of the class /spl diams/S. The proposed solution allows us to replicate a critical server while ensuring that the processing of all the incoming requests is consistent (mechanisms for solving the atomic broadcast problem) and predictable (mechanisms for solving the group priority inversion problem). Thus, the described request scheduling protocol is a key component which can be used to develop fault-tolerant real-time applications in a timed asynchronous system.
6709613
A Nonblocking Approach for Reaching an Agreement on Request Total Orders
In distributed systems that use active replication to achieve robustness, it is important to efficiently enforce consistency among replicas. The nonblocking mode helps to speed up system execution. Unfortunately, this benefit comes at the expense of introducing decision conflicts when the replicas form a single logical token ring and client requests are processed in sequence following the ring. In order to reach an agreement regarding request total orders, this paper proposes a forward-confirmation (FC) approach to identify and solve decision conflicts when up to k successive replicas fail simultaneously. The FC approach can obtain consistent decisions among replicas. An implementation of the FC approach, namely, the queueing method, is proposed. Test results show that our protocol in the nonblocking mode outperforms the Totem protocol regarding delays and failure recovery.
7500432
A Method to Organize A Small-World Based Publish/Subscribe Network In Large-Scale Environment
The paper proposes a Small-World Network Publish/ Subscribe (SWN-P/S) model in large-scale environment, which is a novel Event-based Middleware with Small-World Network (SWN) model. Through connecting brokers into a small world network, SWN-P/S achieves both a strong local clustering and a small average path length among vast brokers. These characteristics help to spread information through the system more rapidly. The paper also put forwards a cloud-partition method to organize brokers in terms of clustering coefficient in SWN. The method is useful to reduce the amount of routing information stored in each broker and to accelerate information dissemination. Comparisons of SWN-P/S with other construction ways for Publish/Subscribe Event-based Middleware show that SWN-P/S is more suitable for building large-scale distributed systems.
15308955
Avoiding priority inversion on the processing of requests by active replicated servers
We consider the priority inversion problem in an actively replicated system. Priority inversion was originally defined in the context of non-replicated systems. Therefore we first introduce the concept of group priority inversion, which extends the concept of (local) priority inversion to the context of a group of processors that perform an actively replicated processing. We then present the properties of a request scheduling protocol to enforce a total ordering for the processing of requests while avoiding group priority inversions. These properties have been implemented in a protocol that relies on a timed asynchronous system model equipped with a failure detector of the class /spl square/S. The proposed solution allows one to replicate a critical server while ensuring that the processing of all the incoming requests is consistent (mechanisms for solving the atomic broadcast problem) and predictable (mechanisms for solving the group priority inversion problem). Thus, the described request scheduling protocol is a key component which can be used to develop fault tolerant real time applications in a timed asynchronous system.
5609348
Non-blocking message total ordering protocol
Message total ordering is a critical part in active replication in order to maintain consistency among members in a fault tolerant group. The paper proposes a non-blocking message total ordering protocol (NBTOP) for distributed systems. Non-blocking property refers to that the members in a fault tolerant group keep on running independently without waiting for installing the same group view when a fault tolerant group evolves even when decision messages collide. NBTOP takes advantage of token ring as its logical control way. Members adopt re-requesting mechanism (RR) to obtain their lost decisions. Forward acknowledgement mechanism (FA) is put forth to solve decision collisions. The paper further proves that NBTOP satisfies the properties of total order, agreement, and termination. NBTOP is implemented, and its performance test is done. Comparing with the performance of Totem, the results show that NBTOP has a better total ordering delay. It manifests that non-blocking property helps to improve protocol efficiency.
17669846
Research on the Robustness of a Proportional Integral Switching Surface Based on Sliding Mode Control
In this paper, a novel proportional-integral (PI) switching surface is introduced for determining the synchronization performance of systems in the sliding mode motion. Based on the sliding mode controller, the system is established by a robust control scheme which guarantees the occurrence of a sliding motion of error states even when the parameter uncertainty and external disturbance are present. So this paper researches on robust synchronization problem by investigating a highly complex dynamic nonlinear system—chaotic systems. Some simulation results on controlling different chaotic systems are made and investigated in order to demonstrate the good performance of the method and this control design process is much easier to be completed.
63568794
Plenary lecture 1: an information flow based model of representation for developing informatics as an academic discipline
In informatics and information systems, a fundamental notion is representation. And yet, it would seem that in the literature of information systems this notion has been taken as self-evident and therefore treated largely intuitively, and in particular, how a possible representational relationship between two systems may be systematically identified and formalized has not been fully addressed. We believe that a mathematical model of representation helps develop informatics as a proper academic discipline. We observe that the notion of representation is formalizable. This is because it is information flow channels that underpin representational relationships between systems. We propose an information flow based model whereby to capture, formalize, analyze and reason about representation for distributed systems. We draw on semantic information theories, which not only lay solid philosophical foundations, but also contribute to forming a mathematical foundation for the model. Regularities is taken as a fundamental principle based upon which an information flow channel is constructed in which both tokens and types of a classification are taken into consideration. We introduce the notion of representation link, which connects classifications (contexts in FCA) through type level constraints and token level connections. Our model enables an analysis of information flow within a distributed system both qualitatively and quantitatively. The channel hierarchy and link hierarchy take into account background information, which enhances inference on representation links. The model allows agents to choose a channel that is the most appropriate for their purposes without violating the objectivity of information flow. 
 
This model is then applied to the problem of semantic interoperability. A semantic integration model is thus built. The process of semantic integration is examined by using the mathematical mechanism of the model. The validity of the model is verified by analyzing results of semantic integration from both content and quantity perspectives, and also by showing that the notion of channel and representation link hierarchy involved in our model helps reason over different but relevant integrations.
41505059
Distributed Computation in Local Area Networks of Workstations
This paper describes the performance analysis of the local area network (LAN) of workstations for distributed computing applications. Several application programs represented in a task graph format are scheduled by the user workstation (master) for parallel execution in the idle or lightly loaded processors (slaves) in LAN. The partial results are collected by the master station to synchronize the operation of slave nodes. The system performance is characterized by the network speedup considering scheduling time, network load and size, communication time, TCP/IP communication overhead, task execution, and synchronization time. The sequential and parallel execution times and the performance degradation factors were measured during the implementation for various network loads. The measurement values and theoretical results have shown that the system performance is degraded mostly by the TCP/IP overhead (0.2 s), the network size, and the network load.
2358468
Human Action Recognition by Semilatent Topic Models
We propose two new models for human action recognition from video sequences using topic models. Video sequences are represented by a novel "bag-of-words" representation, where each frame corresponds to a "word". Our models differ from previous latent topic models for visual recognition in two major aspects: first of all, the latent topics in our models directly correspond to class labels; second, some of the latent variables in previous topic models become observed in our case. Our models have several advantages over other latent topic models used in visual recognition. First of all, the training is much easier due to the decoupling of the model parameters. Second, it alleviates the issue of how to choose the appropriate number of latent topics. Third, it achieves much better performance by utilizing the information provided by the class labels in the training set. We present action classification results on five different data sets. Our results are either comparable to, or significantly better than previously published results on these data sets.
11056640
Two Further Gradient BYY Learning Rules for Gaussian Mixture with Automated Model Selection
Under the Bayesian Ying-Yang (BYY) harmony learning theory, a harmony function has been developed for Gaussian mixture model with an important feature that, via its maximization through a gradient learning rule, model selection can be made automatically during parameter learning on a set of sample data from a Gaussian mixture. This paper proposes two further gradient learning rules, called conjugate and natural gradient learning rules, respectively, to efficiently implement the maximization of the harmony function on Gaussian mixture. It is demonstrated by simulation experiments that these two new gradient learning rules not only work well, but also converge more quickly than the general gradient ones.