Improving the scalability of the CORBA event service with a multi‐agent load balancing algorithm

The event service of the Common Object Request Broker Architecture (CORBA) is useful in supporting decoupled and asynchronous communication between distributed object components. However, the specification of the event service standard does not require implementation to provide facilities to guarantee efficient event/data delivery. Consequently, applications in which a large number of objects need to communicate via an event service channel may suffer from poor performance. In this paper, a generic CORBA‐based framework is proposed to tackle this scalability problem. Two techniques are applied; namely, event channel federation and load balancing. The solution is transparent in the sense that it exports the same IDL interface as the original event service. We explore three critical dimensions underlying the design of the load‐balancing algorithm and conduct experiments to evaluate their impact on the overall performance of the framework. The results provide some useful insights into the improvement of the scalability of the event service. Copyright © 2002 John Wiley & Sons, Ltd.     

An event routing service for distributed applications: computer telephony—a case study

This paper presents an event routing service (ERS) that represents a pattern for the establishment and processing of lightweight sessions between a source and a destination of events. It is based on the CORBA notification service. To illustrate the features of the proposed service, its application in computer telephony is discussed in detail. Most of the positive features of the ERS are inherited from the CORBA notification service, but its implementation requires a novel protocol describing the lightweight session establishment mechanism. The implementation of ERS is described and its application to routing events in a computer telephony system is presented. The paper concludes with a performance measurement study. Copyright © 2002 John Wiley & Sons, Ltd.     

基于EDA-SOA的ERP中的智能通知模型*

为了使用户能从海量事件流中迅速认知有价值事件,提出了一个基于EDA-SOA的智能通知模型。当一个计划外或不属于工作流的事件发生时,事件通知服务根据感知树和决策树的交叉判断决定是否发送事件,保证信息准确且无冗余地通知到相关人。将模型应用于ERP采购子系统,取得了良好的效果。     

CORBA通知服务的特性探讨

在揭示CORBA事件服务局限性的基础上，重点剖析通知服务所实现的新特性，包括事件过滤、服务质量、发布与订阅机制等，并比较了CORBA通知服务与消息中间件的异同，同时指出使用通知服务的方法。     

面向服务环境下的事件通知服务：模型与实现面

事件通知服务设计在面向服务环境下面临更多挑战,例如因特网规模下应用层接口、事件模型的互操作要求更高,事件通信实体与通知订阅的软状态管理等问题。目前,基于业务服务设计面向服务环境下的事件通知服务的工作还很少。本文从抽象的业务服务概念出发,设计并实现的事件通知服务具有事件派发模型独立于事件传输协议和编码、分布的事件通知代理体系结构以及按需派发事件等特点。该系统在项目中的应用表明了大规模动态多变的分布环境下本文设计的事件通知服务的正确性,以及由业务服务抽象带来的灵活性。     

The architecture of an event correlation service for adaptive middleware-based applications

Loosely coupled component communication driven by events is a key mechanism for building middleware-based applications that must achieve reliable qualities of service in an adaptive manner. In such a system, events that encapsulate state snapshots of a running system are generated by monitoring components. Hence, an event correlation service is necessary for correlating monitored events from multiple sources. The requirements for the event correlation raise two challenges: to seamlessly integrate event correlation services with other services and applications; and to provide reliable event management with minimal delay. This paper describes our experience in the design and implementation of an event correlation service. The design encompasses an event correlator and an event proxy that are integrated with an architecture for adaptive middleware components. The implementation utilizes the common-based event (CBE) specification and stateful Web service technologies to support the deployment of the event correlation service in a distributed architecture. We evaluate the performance of the overall solution in a test bed and present the results in terms of the trade-off between the flexibility and the performance overhead of the architecture.     

EFFECTIVE BIO‐EVENT EXTRACTION USING TRIGGER WORDS AND SYNTACTIC DEPENDENCIES

The scientific literature is the main source for comprehensive, up‐to‐date biological knowledge. Automatic extraction of this knowledge facilitates core biological tasks, such as database curation and knowledge discovery. We present here a linguistically inspired, rule‐based and syntax‐driven methodology for biological event extraction. We rely on a dictionary of trigger words to detect and characterize event expressions and syntactic dependency based heuristics to extract their event arguments. We refine and extend our prior work to recognize speculated and negated events. We show that heuristics based on syntactic dependencies, used to identify event arguments, extend naturally to also identify speculation and negation scope. In the BioNLP’09 Shared Task on Event Extraction, our system placed third in the Core Event Extraction Task (F‐score of 0.4462), and first in the Speculation and Negation Task (F‐score of 0.4252). Of particular interest is the extraction of complex regulatory events, where it scored second place. Our system significantly outperformed other participating systems in detecting speculation and negation. These results demonstrate the utility of a syntax‐driven approach. In this article, we also report on our more recent work on supervised learning of event trigger expressions and discuss event annotation issues, based on our corpus analysis.     

基于MQTT的企业消息推送系统

消息推送系统在实现企业办公自动化方面有着重要的作用,通信协议和系统架构的设计是企业消息推送系统性能优化的关键因素.传统的标准化协议方案在移动互联网领域的应用存在着实现复杂和流量消耗大等缺点.针对这一问题,结合企业消息推送系统的特点,采用物联网领域的轻量级协议MQTT来设计企业消息推送系统的通信协议,通过设计MQTT话题区分社交通知、即时消息和状态呈现等功能,在满足了应用需求的同时保证了协议的简单易实现和流量消耗小等适用于移动互联网的优势.另一方面,在传统的对称和非对称设计的服务器架构之上,提出了信息上非对称和功能上对称的系统架构,为企业消息推送系统的构建提供了一个详细的解决方案.该方案在满足系统设计需求的同时提高了系统的可扩展性.     

Twins: A Dual Addressing Space Representation for Self-Organizing Networks

As the size of mobile self-organizing networks increases, the efficiency of location services must increase as well so that addressing/routing scalability does not become an issue. In this paper, we propose a novel architecture, called Twins, tailored for self-organizing networks. Twins architecture involves addressing and locating nodes in large networks, forwarding packets between them, and managing in the presence of mobility/topology changes. Twins defines a logical multidimensional space for addressing and forwarding, while location service and management operations make use of a one-dimensional space. To improve scalability and performance, forwarding is hop-by-hop with greedy next-hop choice and the location service uses a rendezvous paradigm to distribute information among nodes. In this paper, we describe the Twins architecture and present a performance evaluation to assess scalability, fairness in the overhead distribution among nodes, and routing robustness.     

Autonomic configuration and recovery in a mobile agent‐based distributed event monitoring system

In this paper we present a framework for building policy‐based autonomic distributed agent systems. The autonomic mechanisms of configuration and recovery are supported through a distributed event processing model and a set of policy enforcement mechanisms embedded in an agent framework. Policies are event‐driven rules derived from the system's functional and non‐functional requirements. Agents in the network monitor the system state for policy violation conditions, generate appropriate events, and communicate them to other agents for cooperative filtering, aggregation, and handling. A set of agents perform policy enforcement actions whenever events signifying any policy violation conditions occur. Policies are defined using a specification framework based on XML. The policy enforcement agents interpret the policies given in XML. We illustrate the utility of this framework in the context of an agent‐based distributed network monitoring application. We also present an experimental evaluation of our approach. Copyright © 2006 John Wiley & Sons, Ltd.     

Remote service discovery and binding architecture for soft real-time QoS in indoor location-based service

Indoor location-based service (LBS) is generally distinguished from web services that have no physical location and user context. In particular, various resources have dynamic and frequent mobility in indoor environments. In addition, an indoor LBS includes numerous service lookups being requested concurrently and frequently from several locations, even through a network infrastructure requiring high scalability in indoor environments. The traditional centralized LBS approach needs to maintain a geographical map of the entire building or complex in its central server, which can cause low scalability and traffic congestion. This paper presents a self-organizing and fully distributed indoor LBS platform with regional cooperation among devices. A service lookup algorithm based on the proposed distributed architecture searches for the shortest physical path to the nearest service resource. A continuous service binding mechanism guarantees a probabilistic real-time QoS regardless of dynamic and frequent mobility in a soft real-time system such as an indoor LBS. Performance evaluation of the proposed algorithm and platform is compared to the traditional centralized architecture in the experimental evaluation of scalability and real test bed environments.     

数字图书馆中基于内容的事件通知服务的设计与实现

相比于传统的基于主题的事件通知服务，基于内容的事件通知服务提供了更大的灵活性和通用性，订阅者可以根据事件的任意属性来订阅事件，不必受主题的限制．本文从多事件代理组成的分布式结构与事件路由算法、事件代理体系结构和事件过滤算法等多方面论述了数字图书馆中基于内容的事件通知服务CJNS的设计与实现．CJNS在实践中已获得了成功应用。     

基于Globe的分布式LDAP元数据目录服务框架

数据网格应用的发展和规模的扩大对元数据目录服务的可扩展性提出了更高要求。以基于对象的Globe系统为理论模型,提出了一种分布式LDAP元数据目录服务框架,描述了其中的命名服务和定位服务,在定位服务的基础上定义了基本的元数据目录操作。最后对该框架的性能优化和可扩展性进行了详细分析。     

Active optimistic and distributed message logging for message‐passing applications

Message logging is an attractive solution to provide fault tolerance for message‐passing applications because it is more scalable than coordinated checkpointing. Sender‐based message logging is a well‐known optimization that allows the saving of message payload in the sender memory. Thus, only message reception events have to be logged reliably by using an event logger. This paper proposes solutions to further improve message logging protocol scalability. In existing works on message logging, the event logger has always been considered as a centralized process. We propose a distributed event logger that takes advantage of multi‐core processors that are to be executed in parallel with application processes, leveraging the volatile memory of the nodes to save events reliably. We also propose the combination of our distributed event logger and O2P, an active optimistic message logging protocol using a gossip‐based protocol to disseminate information on new stable events. Our distributed event logger and O2P are implemented in the Open MPI library. Our results show the following: (i) distributed event logging improves message logging protocol scalability and (ii) using O2P with a distributed event logger provides an efficient and scalable fault‐tolerant solution for message‐passing applications. Copyright © 2011 John Wiley & Sons, Ltd.     

A loss-event driven scalable fluid simulation method for high-speed networks

Increase of size and bandwidth of computer network posed a research challenge to evaluate proposed TCP/IP protocol and corresponding queuing policies in this scenario. Simulation provides an easier and cheaper method to evaluate TCP proposals and queuing disciplines as compared to experiment with real hardware. In this paper, problem associated with scalability of current simulation method for high-speed network case is discussed. Hence, we present a scalable time-adaptive numerical simulation driven by loss events to represent dynamics of high-speed networks using fluid-based models. The new method uses a loss event to dynamically adjust the size of a time step for a numerical solver which solves a system of differential equations representing dynamics of protocols and nodes’ behaviors. A numerical analysis of the proposed protocol is discussed. A simple simulation of high-speed TCP variants is presented using our method. The simulation results and analysis show that the time-adaptive method reduces computational time while achieving the same accuracy compared to that of a fixed step-size method.     

CoreFlow: Extracting and Visualizing Branching Patterns from Event Sequences

Event sequence datasets with high event cardinality and long sequences are difficult to visualize and analyze. In particular, it is hard to generate a high level visual summary of paths and volume of flow. Existing approaches of mining and visualizing frequent sequential patterns look promising, but have limitations in terms of scalability, interpretability and utility. We propose CoreFlow, a technique that automatically extracts and visualizes branching patterns in event sequences. CoreFlow constructs a tree by recursively applying a three‐step procedure: rank events, divide sequences into groups, and trim sequences by the chosen event. The resulting tree contains key events as nodes, and links represent aggregated flows between key events. Based on CoreFlow, we have developed an interactive system for event sequence analysis. Our approach can compute branching patterns for millions of events in a few seconds, with improved interpretability of extracted patterns compared to previous work. We also present case studies of using the system in three different domains and discuss success and failure cases of applying CoreFlow to real‐world analytic problems. These case studies call forth future research on metrics and models to evaluate the quality of visual summaries of event sequences.     

一种通知服务性能的模糊控制机制

通知服务现已广泛应用于分布式计算当中。通知服务的一个问题是对过载敏感。该文通过分析和仿真研究通知服务的运行性能,得出通知服务的最大允许消费者数与系统的利用率有直接的关系。提出一种通知服务性能的模糊控制机制,对系统的最大允许消费者数进行调节。对该机制进行了仿真实验,实验结果表明模糊控制对通知服务系统负载的变化和系统模型的变化有较强的适应能力,并且对随机负载控制能力比通常的控制器更加有效。     

Constructing scalable Internet of Things services based on their event‐driven models

Even though many IoT (Internet of Things) applications have been implemented based on distributed events, how to construct scalable IoT services is still unclear. In this paper, we first discuss representing physical entities as IoT resources in the cyber world and integrate them into IoT services and then use an event session mechanism to express the coordination logic in an IoT service system. Given their event‐driven models, the scalable IoT services are constructed through decoupling one service at behavior from others, where running atomic service instances with high concurrency is our first focus, and distributed execution of an IoT business process is our second focus. Our last focus is to make each distributed business process execution unit hold its properties in the whole process, which requires modeling the environment as a prerequisite to compute its properties, and some assume‐guarantee rules for composing the services from the environment's perspective. We then propose a platform to support the construction, where according to the behavior decoupling features, one IoT business process is decomposed into pieces of event composition logic and business computation logic, together with separating the data dependency of computation functions in each process fragment, such that it can be concurrently executed and distributed. A practical application is implemented to concept‐prove our work. Copyright © 2015 John Wiley & Sons, Ltd.     

CORBA通知服务在TMN中的应用

构建基于CORBA的TMN是新一代电信网管的发展趋势，其重点是如何将通用的CORBA服务应用于电信网管的专有领域。该文首先介绍了基于COBRA的TMN体系结构，在此基础上详细分析了如何在TMN中应用CORBA通知服务来实现获取事件/通知的管理功能。最后说明了在电信网管中应用通知服务的优势所在。