计算机外文翻译
XX大学毕业设计(文献翻译) 基于J2EE在分布式环境下的底层结构的自动动态配置的应用
Anatoly Akkerman, Alexander Totok, and Vijay Karamcheti
摘要:为了实现广域网中符合工业标准基于组件的应用程序中动态的可适应
性，我们需要一种框架来在这样的环境里自动化地配置J2EE 应用程序。这种需要对于哪怕在单一的应用程序服务器上尝试部署J2EE应用的人来说也显而易见，这种任务设计到大量的系统服务和应用组件的配置。关键词:j2ee;动态配置;分布式;组件;
1 前言
近几年，我们已经看到基于组件的企业应用开发的显著增加。这种应用程序通常被部署在公司的内部网或者是因特网上，以高事务容量，大量的用户和覆盖范围广的访问为特征，它通常会被部署在中央区域，采用服务器集群来均衡负载从而支持用户下载。但是这种平均负荷的方法被证明只对减少应用转发的用户可以察觉的反应时间有效，而对于减少网络方面的延迟作用不大，垂直分割(例如…运行网络层和事务层在不同的虚拟机)被用于错误分离和均衡负荷，但是它是不符合实际的由于远程调运的大量使用显著地增加了运行时时间。最近的著作已经表明在广域网中利用垂直负荷而不引起前面所述的超时问题的可行性。那非研究的主要结论可以概括如下:
(1) 应用合适的应用程序，在广域网中的垂直负荷可以察觉的延迟。
(2) 广域垂直层需要复制应用层组件而且需要维持和原组件间的一致性。
(3) 新加的复制组件可以被动态配置以满足新的需要。
(4) 事实上，不同的复制组件可能会根据应用不同的方式实现相组件。
(5) 新的请求路径可以复用先前的组件配置路径。
应用智能监视和人工智能规划方法再结合那个研究得出的结论，我们看到通过动态布置基于动态监视的额外的应用组件，在广域网中符合工业标准基于组件的应用程序中动态的可适应性是可以实现的。然而，为了实现这种动态可适性，我们需要一种框架来在这样的环境里自动化地配置J2EE 应用程序。这种需要对于哪怕在单一的应用程序服务器上尝试布置J2EE应用的人来说也显而易见，这种任务设计到大量的系统服务和应用组件的配置。例如你必须在配置和部署应用组件前先建立JDBC数据源，设立消息目的地和资源适配器。在需要跨越多个节点服务器的广域网配置中，这将更加复杂，因为
XX大学毕业设计(文献翻译) 更多的便利内部节点通信的系统服务需要配置和启动，而且多种配置数据比如IP地址，端口号，JNDI名字和其他的数据在多个节点的配置文件中必须维持一致性。这种分布式配置框架必须满足:
(1) 声明内部组件一致性规范和定义它对组件配置部署的影响。
(2) 声明应用程序组件对应用服务器，以及它们的配置和部署的依赖性。
(3) 提供简单但可表达的抽象方法去控制通过部署和拆卸组件获得的适用性。
(4) 能够复用服务和组件从而高效的利用网路节点资源。
(5) 提供上述便利而不会增加应用程序员的设计负担。
在本论文中，我们提出自动动态部署J2EE应用程序的框架涉及了上面的所有问题，这种框架为组件定义了结构描述语言，链接说明和集合。这种组件说明语言用来描述应用程序组件和链接，它使得应用组件与系统组件中清晰的分开。一种灵活的系统类型用来定义组件接口和端口的兼容性。一种为配置组件属性而开发的定义和表述语言允许内部组件间独立的规范和组件间属性的继承。组件集合语言允许先前定义的复制的组件通过连接合适的端口集合到应用路径，连接时通过链接复制对象和具体把这些复制组件映射到目标应用服务器节点。组件配置过程评估了应用
程序路径的正确性，确认在系统组件上的应用组件的独立性和完成复制组件的部署。根据这些配置使先前部署的复制组件在新的路径中得以匹配和复用的努力正在做出。我们把这种架构作为JBoss开源java应用服务器的一部分加以实现，在几个J2EE样本程序比如Java PetStore,，RUB和 TPC_W_NYU中进行测试。这种架构实现利用了JBoss的可扩展的微内核结构，基于JMX规范。JBoss的组件结构允许根据部署应用程序的需要增加服务配置。我们相信通过动态部署和拆卸系统服务来重构应用服务器对构建高效资源框架的动态分布部署的J2EE应用程序来说是非常必要的。本文如下部分是这样组织的。第2部分提供了必要的背景以理解和研究有关的J2EE组件技术规范。第3部分对这种架构给出了一般性的描述。第4部分更深入的描述了有关这种架构特别重要的和有趣的内部机制。第五部分描述了如何实现这种架构，相关联的工作将在第六部分介绍。
2 J2EE背景知识
2.1 介绍
XX大学毕业设计(文献翻译)
组件框架。组件框架是一种中间件系统，它支持遵守一定标准的有不同组件构成的应用程序。应用组件被塞入这种确立它们运行环境和规定它们交互的框架中。这通常是通过容器，组件持有者来实现的。这种容器也提供通常需要的功能以实现命名，安全性，事务，和持久性～组件框架为组件的执行提供了一个集成的环境，因此显著的减少了在设计，实现，部署和维护应用程序时工作。现在工业上的组件框架标准以对象管理组的CORBA组件模型， SUN 公司的JAVA 2 Platform J企业版[J2EE]和微软公司的.NET标准，其中在企业里应用最为广泛的组件框架是
2EEE。J2EE. J2EE是开发多层企业应用JAVA程序的综合性的标准。J2EE规范定义如下:
(1) 组件编程模型。
(2) 组件和主服务器的链接。
(3) 服务器提供给组件的服务。
(4) 各种各样的人物角色。
(5) 兼容性检验装置和编译测试程序。
在众多的服务列表中，消息通信，事务处理，命名机制和其它应用组件用到的服务是应用服务器必须提供的。用J2EE进行应用开发必须遵守经典的3层结构—表现层，业务层和企业信息系统层。属于各层的J2EE组件在开发时遵守具体的
J2EE标准。 1、表现层或者网络层
这一层实际上又被分为客户端和服务器端。客户端包括浏览器，applets，Java应用程序等和负责和服务器端的表现层或者业务层进行交互。服务器端包括servlet、jsp和静态网页内容。这些组件负责把业务数据传递给终端用户。数据本身通常从业务层获得有时也从企业信息系统层直接获得。表现层的服务器端通常通过Http协议来进行访问。 2、业务层或者EJB层
这一层包含EJB，即企业应用的事务逻辑模型。这些组件提供了持久化机制和事务支持。EJB中的组件通过RMI被调用。在Java虚拟机调用或者异步的消息传递，取决与EJB组件的类型。EJB规范定义了很多种组件。它们在调用风格(同步和异步，本地和远程)与状态(完全状态，不可持久状态，可持久)方面不同。同步调用的EJB组件通过特定的工厂代理对象来表现自己。这种工厂代理对象通常被EJB部署者绑定在JNDI中。EJB对象允许或者本地EJB对象是特定EJB实例的代理。
3、企业信息系统或者数据层
这一层指的就是企业信息系统，比如关系数据库，ERP系统，消息系统等。业务层
XX大学毕业设计(文献翻译) 和持久层在资源适配器的帮助下与该层进行通
信。资源适配器在Java连结结构中被定义。J2EE编程模型一直被认为是分布式的
编程模型，在该模型中应用组件在J2EE服务器上运行并且彼此可以相互交互。经
过初始化说明和第一个服务实现后，该技术，更显著的说EJB技术，已经明显地从纯粹的分布式计算模型转向了本地交互。转变的背后有合理的性能有关的原因，然而分布式的特征现在还存在。J2EE规范已经经过了好几次修订，现在最稳定的版
本是1.3，1.4版本正处于重审阶段。我们应该把注意力放在1.3版本上，而实际
上是在学习后者。适用与商业的J2EE实现可以大量的从BEA系统，IBM，Oracle
等赞助商得到。包括JBoss和JOnAS在内的开源实现据称兼容性也不错。最近名单上有多出了新的Apache project Geronimo。
2.2 J2EE组件编程模型
在我们基本的J2EE组件前，先让我们强调一下什么是组件。软件组件是有一
系列的具体的接口和明确的上下文环境构成。它可以被独立的部署而且易于被第三方重构。根据以上的定义，如下的组成J2EE应用程序的实体可以看作是软件组件:
(1) EJBS(会话，实体，消息驱动)。
(2) Web组件(Servlet、JSP)。.
(3) 消息目的。
(4) 数据源。
EJB和Web组件被部署在由应用服务赞助商提供的容器中.它们有定义良好的容
器规则来管理生命周期，线程，持久化和其他问题。EJB和Web组件都利用JNDI
目录机制去寻找资源和它们想要交互的其EJB组件。目录被执行的JNDI环境被独
立的由容器的每个组件加以维护。该种环境下的绑定机制通常由组件部署的解释者加以配置。消息目的地，像对话和队列，是由消息服务执行所提供的资源。数据源是提供给应用服务器的为事务组件进入到企业信息服务层提供数据接口，通常由被
应用服务器管理的JDBC连接池实例化。一个J2EE编程者明确编写的项目只有EJB 和Web组件。这些用户编写的组件彼此交互而且系统服务可以是明显的也可以是隐含的。例如，EJB开发者可以选择明确的事务区分方式，这种方式意味着开发者假设通过定义良好接口的事务经理服务平台来书写明确的程序交互。或者，开发者也可选择容器管理事务区分的方式。这样由于组件的事务行为通过他的描述者来定义而且全部用EJB容器来处理，因此作为一个隐式独立的EJB提供潜在的事务管理服务。
XX大学毕业设计(文献翻译) 2.3 组件间的链接
2.3.1 远程交互
J2EE仅定义了三种可以在不同应用服务器间传递的基本组件间连接类型。在这三种情况下，通信通过特定的Java对象来完成。
(1) 远程EJB调用:同步的EJB调用通过主EJB对象和EJB对象接口来实现。
(2) Java连结器的外部连接:同步消息接收，同步和异步消息发送，用连接工厂和连接接口进行数据库查询。
(3) Java连接器的内部连接:异步消息传递进入消息驱动Bean只能使用Activation Spec 对象。
在前两个实例中，应用组件的开发者不仅书写执行在组件的运行时JNDI环境中的对象目录代码，而且书写发布方法调用，与远程的组件相互发送和接受消息。组件的运行时JNDI环境为每一个组件部署所创建。环境中的绑定在组件部署时由部署者进行初始化。这些绑定被假设为是静态的，因为规格中没有提供任何的容器和组件间协议去提示绑定发生了变化。在 Java连接器的内部通信情景下，Activation Spec 对象查询以及所有的相应的M容器隐式的完成。虽然查询的协议还没有被标准化，但是假设一个基于JMX或者JNDI的查询是合理的。假设潜在的
应用服务器提供了所有的设备去控制部署过程的每一步，那么在两个J2EE组件间确立一个连接需要涉及:
(1) 部署目标组件类。
(2) 创建一个特定的Java对象用作目标组件代理。
(3) 用组件的命名服务去绑定目标。
(4) 启动目标组件。
(5) 部署指定的组件类。
(6) 在主机的命名服务中，创建和进行指定组件的运行环境。
(7) 启动指定的组件。
然而，没有一个现代的应用服务器允许详细的控制所有组件类型的部署过程除了在它们的部署解释器中的有限的选择。因此我们的架构将使用简化的途径，它所依赖的特征在现在的大多数的应用服务器上都可以得到。
(1) 动态部署消息目的和数据源的能力。
(2) 创建和绑定特定的JNDI目标去访问消息目的和数据源的能力。
XX大学毕业设计(文献翻译)
(3) 把初始绑定的EJB对象到EJB部署组件的能力。
(4) 用在参考组件运行环境中的JNDI指引去指出绑定的参考EJB的能力。在只有相同的应用服务器的架构中，上面的功能对通过简单的部署控制解释器方式来控件间的连接已经足够了。然而，在不同应用服务器的环境下，由于跨服务器的类下载问题，这种简单的控制解释器的方式是不够的。
2.3.2 本地交互
一些组件间的交互可以发生在同一地点的相同应用服务器虚拟机的组件间，有时候甚至可以发生在只有相同容器的组件间。在Web层，这种交互的例子是servlet到 servlet的请求转发。在EJB层，这种交互的例子是CMP实体关系和通
过EJB本地接口的调用。这种本地部署所关心的不是在分布式架构中去表现而是去增强一致性。因此，这种架构把所有的本地的组件请求当作一个单一的组件加以对待。
2.4 部署J2EE应用程序和系统服务
2.4.1 部署应用程序组件
部署和拆卸标准的J2EE组件还没有统一的标准，因此每个应用服务的提供商对组件的部署和拆卸提供了单独的功能于J2EE规范中没有定义标准组件的包，包的格式和包内的基于xml部署解释器的位置，因此这种包对于没有所属权变化的应用服务器不需要部署。具体变化的例子有:
(1) 支持或者取代标准所有者解释器的新的所有者解释器的产生。
(2) 具体服务应用程序类的代码的更替。
为了着手构建一个能够部署不可网络的动态的分布式的架构，我们提出了一种普遍的部署单元即一个简单的基于xml部署的解释器或者是一组类似的绑定到文档中的解释器。文档可能包含用于执行组件的Java类或者任何其它的所需组件。相应地，部署解释器也可以简单地用URL来索引代码。我们假设这种动态的部署和拆卸服务存在于所有的兼容的J2EE服务器上而且在不理解类重载相关问题时一个健壮的类重载结结构的应用服务器就能够重复的部署生命周期。大多数现代的应用服务器都提供这样的功能。 2.4.2 部署系统组件
对应用组件来说，J2EE规范只是少了在部署和拆卸时的明确定义，而对系统服务
XX大学毕业设计(文献翻译) 来说，在这方面做的更糟。对系统服务来说不仅没有具体的定义一个标准化的部署，实际上，这个规格甚至连没有强调在生命周期属性方面的要求，更不用手强调依赖也潜在的系统服务的应用组件的明确规范了取而代之的是它定义了部署者的角色，这个角色负责确保像组件的本性和系统的解释
器所暗示的那样，所需的服务是基于应用组件对系统服务依赖性的基础之上。例如，假如有一个事务容器要至少用一种方法去开始一个新的事务，那么一个带有这样的事务容器的EJB就需要在应用层表示事务管理服务。与之相似的是，一个消息驱动的bean，也隐式需要一种运行在网络上消息服务实例。它为MDB管理消息目的以及基于查询的Java连接器通过它的管理服务层去提供这种消息服务。考虑到应用层可能通常只用到了应用服务器所提供的服务的一个子集，根据应用层的需要允许递增的配置服务的组件应用服务器允许更高效的利用多种资源。包括，开源的应用服务器，JBoss和OnAS在内，已经有多种J2EE应用服务器已经全部或者部分的实现了组件化。我们感觉到通过动态的部署和拆卸系统服务，动态的配置应用服务器对动态分布的部署J2EE应用程序是一种十分重要的构建资源有效型框架的方法。因此我们提倡并将把用JBoss应用服务器设计的微内核的应用服务器用作一个模型。在该模型中，一个微型的服务包括了系统调用总线，一个稳健的类下载子系统，一些命名子系统和一个动态配置子系统。所有其它的服务是热部署并且通过一个普通的调用总线来进行通信。例如，JBoss利用Java管理扩展服务器来实现基本的命名和调用功能。除此之外，JBoss实现了一个先进的类下载子系统和部署服务。所有其它的JBoss是动态配置的，并外在的表现为具有良好机制和生命周期的JMX MBeans.这样的一种应用服务器根据系统服务外在利用应用组件去设计相关功能，并且只有需要的系统服务才会得到合理配置和部署～
参考文献
[1] Matt Bishop. Computer Security: Art and Science. New York, 2002
[2] Matt Bishop. Vulnerabilities Analysis. Proceedings of the Second International Symposium on Recent
Advances in Intrusion Detection. Los Angeles 2006
[3] Balasubra maniyan. Architecture for Intrusion Detection using Autonomous Agents[M]. Department of
Computer Sciences, Purdue University, 1998.
XX大学毕业设计(文献翻译)
Infrastructure for Automatic Dynamic Deployment
Of J2EE Application in Distributed Environments
Anatoly Akkerman, Alexander Totok, and Vijay Karamcheti
Abstract: in order to achieve such dynamic adaptation, we need an infrastructure for automating J2EE application deployment in such an environment. This need is quite evident to anyone who has ever tried deploying a J2EE application even on a single application server, which is a task that involves a great deal of configuration of both the system services and application components.
Key words: j2ee; component; Distributed; Dynamic Deployment;
1 Introduction
In recent years, we have seen a significant growth in component-based enterprise application development. These applications are typically deployed on company Intranets or on the Internet and are characterized by high transaction volume, large numbers of users and wide area access. Traditionally they are deployed in a central location, using server clustering with load balancing (horizontal partitioning) to sustain user load. However, horizontal partitioning has been shown very efficient only in reducing application-related overheads of user-perceived response times, without having much effect on network-induced
latencies. Vertical partitioning (e.g., running web tier and business
tier in separate VMs) has been used for fault isolation and load balancing but it is sometimes impractical due to significant run-time overheads (even if one would keep the tiers on a fast local-area network) related to heavy use of remote invocations. Recent work [14] in the context of J2EE component based applications has shown viability of vertical partitioning in wide-area networks without incurring the aforementioned overheads. The key conclusions from that study can be summarized as follows:
? Using properly designed applications, vertical distribution across wide-area networks
improves user-perceived latencies.
? Wide-area vertical layering requires replication of application components and maintaining consistency between replicas.
? Additional replicas may be deployed dynamically to handle new requests.
? Different replicas may, in fact, be different implementations of
the same component based on usage (read-only, read-write).
XX大学毕业设计(文献翻译)
? New request paths may reuse c omponents from previously deployed paths.
Applying intelligent monitoring [6] and AI planning [2, 12] techniques in conjunction with the conclusions of that study, we see a
potential for dynamic adaptation in industry-standard J2EE component-based applications in wide area networks
Through deployment of additional application components dynamically based on active monitoring. However, in order to achieve such dynamic adaptation, we need an infrastructure for automating J2EE application deployment in such an environment. This need is quite evident to anyone who has ever tried deploying a J2EE application even on a single application server, which is a task that involves a great deal of configuration of both the system services and application components. For example one has to set up JDBC data sources, messaging destinations and other resource adapters before application components can be configured and deployed. In a wide area deployment that spans multiple server nodes, this proves even more complex, since more system services that facilitate inter-node communications need to be configured and started and a variety of configuration data, like IP addresses, port numbers, JNDI names and others have to be consistently maintained in various configuration files on multiple nodes.
This distributed deployment infrastructure must be able to:
? address inter-component connectivity specification and define its effects on component configuration and deployment,
? address application component dependencies on applica tion server services, their
configuration and deployment,
? provide simple but expressive abstractions to control adaptation through dynamic deployment and undeployment of components, ? enable reuse of services and components to maintain efficient use
o f network nodes’ resources,
? provide these facilities without incurring significant additional design effort on behalf of application programmers.
In this paper we propose the infrastructure for automatic dynamic deployment of J2EE applications, which addresses all of the aforementioned issues. The infrastructure defines architecture
description languages (ADL) for component and link description and assembly.
XX大学毕业设计(文献翻译)
The Component Description Language is used to describe application components and links. It provides clear separation of application components from system components. A flexible type system is used to define compatibility of component ports and links. A declaration and expression language for configurable component properties allows for specification of inter-component dependencies and propagation of properties between components. The Component (Replica) Assembly Language allows for assembly of replicas of previously defined components into application paths by
Connecting appropriate ports via link replicas and specifying the mapping of these component replicas onto target application server nodes.
The Component Configuration Process evaluates an application path’s correctness, identifies the dependencies
of application components on system components, and configures component replicas for deployment. An attempt is made to match and reuse any previously deployed replicas in the new path based on their configurations. We implement the infrastructure as a part of the JBoss open source Java application server [11] and test it on several Sample J2EE applications – Java Pets tore [23], Rubies [20] and
TPC-W-NYU [32]. The
infrastructure implementation utilizes the JBoss’s extendable
micro-kernel architecture, based
on the JMX [27] specification. Componentized architecture of JBoss allows incremental service deployments depending on the needs of deployed applications. We believe that dynamic reconfiguration of application servers through dynamic deployment and undeployment of system services is essential to building a resource-efficient framework for dynamic distributed deployment of J2EE applications. The rest of the paper is organized as follows. Section 2 provides necessary background for understanding the specifics of the J2EE component technology which are relevant to this study. Section 3 gives a general description of the infrastructure architecture, while section 4 goes deeper in describing particularly important and interesting internal mechanisms of the infrastructure. Section 5 describes the implementation of the framework, and related work is discussed in section 6. 2 J2EE Background
2.1 Introduction
Component frameworks. A component framework is a middleware system that supports
applications consisting of components conforming to certain standards. Application
XX大学毕业设计(文献翻译)
components are ―plugged‖ into the component framework, which establishes their environmental conditions and regulates the interactions between them. This is usually done through containers, component holders, which also provide commonly required support for naming, security, transactions, and persistence. Component frameworks provide an integrated environment for component execution, as a result significantly reduce the effort .it takes to design, implement, deploy, and maintain applications. Current day industry component framework standards are represented by Object Management Group’s CORBA Component Model [18], Sun Microsystems’ Java 2 Platform Enterprise Edition (J2EE) [25] and Microsoft’s .NET [17], w ith J2EE being currently the most popular and widely used
component framework in the enterprise arena.
J2EE. Java 2 Platform Enterprise Edition (J2EE) [25] is a comprehensive standard for developing multi-tier enterprise Java applications. The J2EE specification among other things defines the following:
? Component programming model,
? Component contracts with the hosting server,
? Services that the platform provides to these components,
? Various human roles,
? Compatibility test suites and complian ce testing procedures.
Among the list of services that a compliant application server must provide are messaging, transactions, naming and others that can be used by the application components. Application developed using J2EE adhere
to the classical 3-Tier architectures – Presentation Tier, Business Tier, and Enterprise Information System (EIS) Tier (see Fig.
1). J2EE components belonging to each tier are developed adhering to the
Specific J2EE standards.
1. Presentation or Web tier.
This tier is actually subdivided into client and server sides. The client side hosts a web browser, applets and Java applications that communicate with the server side of presentation tier or the business tier. The server side hosts Java Servlet components [30], Java Server Pages (JSPs) [29] and static web content. These components are responsible for presenting business data to the end users. The data
itself is typically acquired from the business tier and
XX大学毕业设计(文献翻译)
sometimes directly from the Enterprise Information System tier. The server side of the presentation tier is typically accessed through
HTTP(S) protocol.
2. Business or EJB tier.
This tier consists of Enterprise Java Beans (EJBs) [24] that model
the business logic of the enterprise application. These components provide persistence mechanisms and transactional support. The components in the EJB tier are invoked through remote invocations (RMI), in-JVM invocations or asynchronous message delivery, depending on the type of EJB component. The EJB specification defines several types of components. They differ in invocation style (synchronous vs. asynchronous, local vs. remote) and statefulness: completely stateless (e.g., Message-Driven Bean), stateful non-persistent
(e.g., Stateful Session Bean), stateful persistent (e.g., Entity Bean). Synchronously invocable EJB components expose themselves through
a special factory proxy object (an EJB Home object, which is specific to a given EJB), which is typically bound in JNDI by the deployer of the EJB. The EJB Home object allows creation or location of an EJB Object, which is a proxy to a particular instance of an EJB 1.
3. Enterprise Information System (EIS) or Data tier.
This tier refers to the enterprise information systems, like
relational databases, ERP systems, messaging systems and the like. Business and presentation tier component communicate with this tier with the help of resource adapters as defined by the Java Connector Architecture [26].The J2EE programming model has been conceived as a distributed programming model where application components would run in
J2EE servers and communicate with each other. After the initial introduction and first server implementations, the technology, most
notably, the EJB technology has seen some a significant shift away from purely distributed computing model towards local interactions 2. There were very legitimate performance-related reasons behind this shift, however the
Distributed features are still available. The J2EE specification has seen several revisions, the latest stable being version 1.3, while version 1.4 is going through last review phases 3. We shall focus our attention on the former, while actually learning from the latter. Compliant commercial J2EE implementations are widely available from BEA Systems [4], IBM [9], Oracle [21] and other vendors. Several open source implementations, including JBoss [11]
XX大学毕业设计(文献翻译)
and JOnAS [19] claim compatibility as well. A
Recent addition to the list is a new Apache project Geronimo [1].
2.2 J2EE Component Programming Model
Before we describe basic J2EE components, let’s first address the issue of defining what a
component is a software component is a unit of composition with contractually specified interfaces and explicit context dependencies only. A software component can be deployed independently and is subject to composition by third parties [31].According to this definition the following entities which make up a typical J2EE application would be considered application components (some exceptions given below): ? EJBs (session, entity, message-driven),
? Web components (servlets, JSPs),
? messaging destinations,
? Data sources,
EJB and Web components are deployed into their corresponding containers provided by the application server vendor. They have well-defined contracts with their containers that govern lifecycle, threading, persistence and other concerns. Both Web and EJB components use JNDI lookups to locate resources or other EJB components they want to communicate with. The JNDI context in which these lookups are performed is maintained separately for each component by its container. Bindings messaging destinations, such as topics and queues, are resources
provided by a messaging service implementation. Data sources are resources provided by the application server for data access by business components into the enterprise information services (data) tier, and most commonly are exemplified by JDBC connection pools managed by the application
Server. A J2EE programmer explicitly programs only EJBs and Web components. These custom-written components interact with each other and system services both implicitly and explicitly. For example, an EJB developer may choose explicit transaction demarcation (i.e., Bean-Managed Transactions) which means that the developer assumes the burden of writing explicit programmatic interaction with the platform’s Transaction Manager Service through
well-defined interfaces. Alternatively, the developer may choose Container-Managed transaction demarcation, where transactional behavior of a component is defined through its
XX大学毕业设计(文献翻译)
descriptors and handled completely by the EJB container, thus acting as an implicit dependency of the EJB on the underlying Transaction Manager service.
2.3 Links Between Components
2.3.1 Remote Interactions
J2EE defines only three basic inter-component connection types that can cross application server boundaries, in all three cases; communication is accomplished through special Java objects.
? Remote EJB invocation: synchronous EJB invocati ons through EJB Home and EJB Object interfaces.
? Java Connector outbound connection: synchronous message receipt, synchronous and asynchronous message sending,
Database query using Connection Factory and Connection interfaces.
? Java Connector inbound connection: asynchronous message delivery
into Message-Driven Beans (MDBs) only, utilizing Activation Spec objects. In the first two cases, an application component developer writes the code that performs lookup of these objects in the component’s run-time JNDI context as well as code that issues method invocations or sends and receives messages to and from the remote component. The component’s
run-time JNDI
Talking about security loopholes Richard S. Kraus reference to the core network security business objective is to protect the sustainability of the system and data security, This two of the main threats come from the worm outbreaks, hacking attacks, denial of service attacks, Trojan horse. Worms, hacker attacks problems and loopholes closely linked to, if there is major security loopholes have emerged, the entire Internet will be faced with a major challenge. While traditional Trojan and little security loopholes, but recently many Trojan are clever use of the IE loophole let you browse the website at unknowingly were on the move. Security loopholes in the definition of a lot, I have here is a popular saying: can be used to stem the "thought" can not do, and are safety-related deficiencies. This shortcoming can be a matter of design, code realization of the problem. Different perspective of security loo phole s In the classification of a specific procedure is safe from the many loopholes in classification. 1. Classification from the user groups: ● Public loopholes in the software category. If the loopholes in Windows, IE loophole, and so on. ● specialized software loophole. If Oracle loopholes, Apach e,
微软Visual Studio 1微软Visual Studio Visual Studio 是微软公司推出的开发环境，Visual Studio可以用来创建Windows平台下的Windows应用程序和网络应用程序，也可以用来创建网络服务、智能设备应用程序和Office 插件。Visual Studio是一个来自微软的集成开发环境IDE，它可以用来开发由微软视窗，视窗手机，Windows CE、.NET框架、.NET精简框架和微软的Silverlight支持的控制台和图形用户界面的应用程序以及Windows窗体应用程序，网站，Web应用程序和网络服务中的本地代码连同托管代码。 Visual Studio包含一个由智能感知和代码重构支持的代码编辑器。集成的调试工作既作为一个源代码级调试器又可以作为一台机器级调试器。其他内置工具包括一个窗体设计的GUI应用程序，网页设计师，类设计师，数据库架构设计师。它有几乎各个层面的插件增强功能，包括增加对支持源代码控制系统（如Subversion和Visual SourceSafe）并添加新的工具集设计和可视化编辑器，如特定于域的语言或用于其他方面的软件开发生命周期的工具（例如Team Foundation Server的客户端：团队资源管理器）。 Visual Studio支持不同的编程语言的服务方式的语言，它允许代码编辑器和调试器（在不同程度上）支持几乎所有的编程语言，提供了一个语言特定服务的存在。内置的语言中包括C/C + +中（通过Visual C++）,https://www.doczj.com/doc/1a6734810.html,（通过Visual https://www.doczj.com/doc/1a6734810.html,），C＃中（通过Visual C＃）和F＃（作为Visual Studio 2010），为支持其他语言，如M,Python,和Ruby等，可通过安装单独的语言服务。它也支持的 XML/XSLT,HTML/XHTML ,JavaScript和CSS.为特定用户提供服务的Visual Studio也是存在的：微软Visual Basic，Visual J＃、Visual C＃和Visual C++。 微软提供了“直通车”的Visual Studio 2010组件的Visual Basic和Visual C＃和Visual C + +，和Visual Web Developer版本，不需任何费用。Visual Studio 2010、2008年和2005专业版，以及Visual Studio 2005的特定语言版本（Visual Basic、C++、C＃、J＃），通过微软的下载DreamSpark计划，对学生免费。 2架构 Visual Studio不支持任何编程语言，解决方案或工具本质。相反，它允许插入各种功能。特定的功能是作为一个VS压缩包的代码。安装时，这个功能可以从服务器得到。IDE提供三项服务：SVsSolution，它提供了能够列举的项目和解决方案; SVsUIShell，它提供了窗口和用户界面功能（包括标签，工具栏和工具窗口）和SVsShell，它处理VS压缩包的注册。此外，IDE还可以负责协调和服务之间实现通信。所有的编辑器，设计器，项目类型和其他工具都是VS压缩包存在。Visual Studio 使用COM访问VSPackage。在Visual Studio SDK中还包括了管理软件包框架(MPF)，这是一套管理的允许在写的CLI兼容的语言的任何围绕COM的接口。然而，MPF并不提供所有的Visual Studio COM 功能。
计算机网络新技术外文翻译文献 (文档含中英文对照即英文原文和中文翻译) 译文: 计算机网络新技术 摘要 21世纪是一个信息时代的经济，计算机网络技术是这个时期的代表技术，以非常快的、具创造性得不断地发展，并将深入到人民群众的工作，生活和学习中。因此，控制这种技术看起来似乎具有很重要的意义。现在，我主要是采用新技术的几种网络技术在现实生活的应用。 关键字 因特网数字证书数字银包网格存储 3G
1.前言 互联网满36岁，仍然是一个进展中的工作。36年后在加州大学洛杉矶分校的计算机科学家使用15英尺的灰色电缆连接两台笨重的电脑，测试了一种在网络上新的数据交换的方式，这将最终成为互联网依然是一个在取得进展的工作。 大学的研究人员正在试验如何提高网络容量和速度。编程人员正在设法为网页注入更多的智能。并正在进行重新设计网络以减少垃圾邮件（垃圾邮件）和安全麻烦的工作。 与此同时威胁织机：批评人士警告说，商业，法律和政治压力可能会阻碍一些使互联网发展到今天的创新的类型。 斯蒂芬克罗克和温顿瑟夫属于1969年9月2日研究生加入的加州大学洛杉矶分校斯莱昂兰罗克教授工程实验室的团体，作为位无意义的测试数据两台计算机之间默默流动。到第二年的1月，其他三个“节点”加入到了这个网络。 然后是电子邮箱，几年之后，在七十年代后期一个所谓的核心通信协议即TCP / IP 协议，在80年代域名系统和在1990年万维网-现在的第二个最流行的应用背后电子邮件出现了。互联网的扩大，超出其最初的军事和教育领域延伸到了企业和全球的家庭中。 今天，克罗克仍然为互联网工作，为协作设计更好的工具。作为互联网管理机构的安全委员会主席，他正试图保卫系统的核心处理免受来自外部的威胁。 他认识到，他帮助建立的互联网工作远未完成，而这些改变是在商店，以满足多媒体日益增长的需求。网络供应商现唯一的“最佳努力”是在提供的数据包上。克罗克说，需要有更好的保障，以防止跳过和过滤现在常见的视频。 瑟夫，现在在MCI公司说，他希望他建立了有内置安全的互联网。微软，雅虎和美国在线公司，和其他的一些，目前正在努力改进网络，使邮件发送者可以验证的方式发送以降低使用虚假地址发送垃圾邮件。 瑟夫说，现在正在制定许多功能，是不可能立即解决计算速度慢和互联网管道窄，或
外文文献翻译（译成中文2000字左右）： As research laboratories become more automated,new problems are arising for laboratory managers.Rarely does a laboratory purchase all of its automation from a single equipment vendor. As a result,managers are forced to spend money training their users on numerous different software packages while purchasing support contracts for each. This suggests a problem of scalability. In the ideal world,managers could use the same software package to control systems of any size; from single instruments such as pipettors or readers to large robotic systems with up to hundreds of instruments. If such a software package existed, managers would only have to train users on one platform and would be able to source software support from a single vendor. If automation software is written to be scalable, it must also be flexible. Having a platform that can control systems of any size is far less valuable if the end user cannot control every device type they need to use. Similarly, if the software cannot connect to the customer’s Laboratory Information Management System (LIMS) database,it is of limited usefulness. The ideal automation software platform must therefore have an open architecture to provide such connectivity. Two strong reasons to automate a laboratory are increased throughput and improved robustness. It does not make sense to purchase high-speed automation if the controlling software does not maximize throughput of the system. The ideal automation software, therefore, would make use of redundant devices in the system to increase throughput. For example, let us assume that a plate-reading step is the slowest task in a given method. It would make that if the system operator connected another identical reader into the system, the controller software should be able to use both readers, cutting the total throughput time of the reading step in half. While resource pooling provides a clear throughput advantage, it can also be used to make the system more robust. For example, if one of the two readers were to experience some sort of error, the controlling software should be smart enough to route all samples to the working reader without taking the entire system offline. Now that one embodiment of an ideal automation control platform has been described let us see how the use of C++ helps achieving this ideal possible. DISCUSSION C++: An Object-Oriented Language Developed in 1983 by BjarneStroustrup of Bell Labs,C++ helped propel the concept of object-oriented programming into the mainstream.The term ‘‘object-oriented programming language’’ is a familiar phrase that has been in use for decades. But what does it mean? And why is it relevant for automation software? Essentially, a language that is object-oriented provides three important programming mechanisms:
毕业设计(论文)外文资料翻译 系：信息工程学院 专业：计算机科学与技术 姓名： 学号： 外文出处：Chris Haseman. Android-essential (用外文写) s[M].London:Spring--Verlag,2008 .8-13. 附件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 签名： 年月日注：请将该封面与附件装订成册。
附件1：外文资料翻译译文 无线局域网 一、为何使用无线局域网络 对于局域网络管理主要工作之一，对于铺设电缆或是检查电缆是否断线这种耗时的工作，很容易令人烦躁，也不容易在短时间内找出断线所在。再者，由于配合企业及应用环境不断的更新与发展，原有的企业网络必须配合重新布局，需要重新安装网络线路，虽然电缆本身并不贵，可是请技术人员来配线的成本很高，尤其是老旧的大楼，配线工程费用就更高了。因此，架设无线局域网络就成为最佳解决方案。 二、什么情形需要无线局域网络 无线局域网络绝不是用来替代有限局域网络，而是用来弥补有线局域网络之不足，以达到网络延伸之目的，下列情形可能须要无线局域网络。 ●无固定工作场所的使用者 ●有线局域网络架设受环境限制 ●作为有线局域网络的备用系统 三、无线局域网络存取技术 目前厂商在设计无线局域网络产品时，有相当多种存取设计方式，大致可分为三大类：窄频微波技术、展频(Spread Spectrum)技术、及红外线(Infrared)技术，每种技术皆有其优缺点、限制及比较，接下来是这些技术方法的详细探讨。 1.技术要求 由于无线局域网需要支持高速、突发的数据业务，在室内使用还需要解决多径衰落以及各子网间串扰等问题。具体来说，无线局域网必须实现以下技术要求： 1)可靠性：无线局域网的系统分组丢失率应该低于10-5，误码率应该低 于10-8。
附录A With the new network technology and application of the continuous rapid development of the computer network should. Use of becoming increasingly widespread, the role played by the increasingly important computer networks and human. More inseparable from the lives of the community's reliance on them will keep growing. In order for computers to communicate, they must speak the same language or protocol. In the early days of networking, networks were disorganized in many ways. Companies developed proprietary network technologies that had great difficulties in exchanging information with other or existing technologies; so network interconnections were very hard to build. To solve this problem, the International Organization for Standardization（ISO）created a network model that helps vendors to create networks compatible with each other. Finding the best software is not easy. A better understanding of what you need and asking the right questions makes it easier. The software should be capable of handling challenges specific to your company. If you operate multiple distribution centers, it may be beneficial to create routes with product originating from more than one depot. Few software providers though, are capable of optimizing routes using multiple depots. The provider should be able to support installation of its product. Make sure to clearly understand what training and software maintenance is offered. Obviously, selecting the right routing/scheduling software is critically important. Unfortunately, some companies are using software that may not be best suited to their operation. Logistics actives with responsibility for approving the software ought to be comfortable they've made the right decision. It is important to realize that not all routing/scheduling software is alike！ There questions to ask are：Which operating system is used？How easy is the software to use？Here is a good way to tell. Ask if its graphical user interface（GUI）is flexible. Find out about installation speed - how long does it take？Is the software able to route third party customers with your core business？When was the software originally released and when was it last upgraded？ In 1984, ISO released the Open Systems Interconnection（OSI）reference model,
专业外文翻译 题目JSP Technology Conspectus and Specialties 系（院）计算机系 专业计算机科学与技术 班级 学生姓名 学号 指导教师 职称讲师 二〇一三年五月十六日
JSP Technology Conspectus and Specialties The JSP (Java Server Pages) technology is used by the Sun micro-system issued by the company to develop dynamic Web application technology. With its easy, cross-platform, in many dynamic Web application programming languages, in a short span of a few years, has formed a complete set of standards, and widely used in electronic commerce, etc. In China, the JSP now also got more extensive attention; get a good development, more and more dynamic website to JSP technology. The related technologies of JSP are briefly introduced. The JSP a simple technology can quickly and with the method of generating Web pages. Use the JSP technology Web page can be easily display dynamic content. The JSP technology are designed to make the construction based on Web applications easier and efficient, and these applications and various Web server, application server, the browser and development tools work together. The JSP technology isn't the only dynamic web technology, also not the first one, in the JSP technology existed before the emergence of several excellent dynamic web technologies, such as CGI, ASP, etc. With the introduction of these technologies under dynamic web technology, the development and the JSP. Technical JSP the development background and development history In web brief history, from a world wide web that most of the network information static on stock transactions evolution to acquisition of an operation and infrastructure. In a variety of applications, may be used for based on Web client, look no restrictions. Based on the browser client applications than traditional based on client/server applications has several advantages. These benefits include almost no limit client access and extremely simplified application deployment and management (to update an application, management personnel only need to change the program on a server, not thousands of installation in client applications). So, the software industry is rapidly to build on the client browser multilayer application. The rapid growth of exquisite based Web application requirements development of
附录 一、英文原文： The NetWorks Birth of the Net The Internet has had a relatively brief, but explosive history so far. It grew out of an experiment begun in the 1960's by the U.S. Department of Defense. The DoD wanted to create a computer network that would continue to function in the event of a disaster, such as a nuclear war. If part of the network were damaged or destroyed, the rest of the system still had to work. That network was ARPANET, which linked U.S. scientific and academic researchers. It was the forerunner of today's Internet. In 1985, the National Science Foundation (NSF) created NSFNET, a series of networks for research and education communication. Based on ARPANET protocols, the NSFNET created a national backbone service, provided free to any U.S. research and educational institution. At the same time, regional networks were created to link individual institutions with the national backbone service. NSFNET grew rapidly as people discovered its potential, and as new software applications were created to make access easier. Corporations such as Sprint and MCI began to build their own networks, which they linked to NSFNET. As commercial firms and other regional network providers have taken over the operation of the major Internet arteries, NSF has withdrawn from the backbone business. NSF also coordinated a service called InterNIC, which registered all addresses on the Internet so that data could be routed to the right system. This service has now been taken over by Network Solutions, Inc., in cooperation with NSF. How the Web Works The World Wide Web, the graphical portion of the Internet, is the most popular part of the Internet by far. Once you spend time on the Web,you will begin to feel like there is no limit to what you can discover. The Web allows rich and diverse communication by displaying text, graphics, animation, photos, sound and video. So just what is this miraculous creation? The Web physically consists of your personal computer, web browser software, a connection to an Internet service provider, computers called servers that host digital data and routers and switches to direct the flow of information. The Web is known as a client-server system. Your computer is the client; the remote computers that store electronic files are the servers. Here's how it works: Let's say you want to pay a visit to the the Louvre museum website. First you enter the address or URL of the website in your web browser (more about this shortly). Then your browser requests the web page from the web server that hosts the Louvre's site. The Louvre's server sends the data over the Internet to your computer. Your web
计算机专业外文文献及翻译 微软Visual Studio 1微软Visual Studio 是微软公司推出的软软软境～可以用软建来平台下的 Visual Studio Visual StudioWindows 软用程序和软软用程序～也可以用软建软服软、智能软软软用程序和网来网 插件。WindowsOffice Visual 是一自微软的个来集成软软软境;,～可以用软软由它来微StudioIDEinteqrated development environment软软窗～软手机窗～、框架、精软架框和微软的支持的控制台和软Windows https://www.doczj.com/doc/1a6734810.html,Silverlight 形用软界面的软用程序以及窗体软用程序～站网～软用程序和软服软网中的本地代软软同托管WindowsWeb 代软。 包含一由个智能感知和代软重构支持的代软软软器。集成的软软工作作软一源代软软软既个Visual Studio 软器又可以作软一台机器软软软器。其他置工具包括一软软内个窗体的软用程序～软软软软～软软软软～网数据软架GUI 构软软软。有乎各软面的件增强功能～包括增加软支持它几个插源代软控制系软;如和SubversionVisual ,添加新的工具集软软和可软化软软器～如并特定于域的软言或用于其他方面的软件软软生命周期SourceSafe 的工具;例如的客软端,软软软源管理器,。Team Foundation Server
支持不同的软程软言的服软方式的软言～允软代软软软器和软软器;在不同程 度上,支持它Visual Studio 几乎所有的软程软言～提供了一软言特定服软的存在。置的软言中包括个内中;通软C/C + +Visual C+,;通软,～,中;通软,,和,;作软+,https://www.doczj.com/doc/1a6734810.html,Visual https://www.doczj.com/doc/1a6734810.html,CVisual CFVisual Studio ,～软支持其他软言～如和等～可通软安软的软言服软。软也支持装独它的2010M,Python,Ruby 和软特定用软提供服软的也是存在的,微 XML/XSLT,HTML/XHTML ,JavaScriptCSS.Visual Studio软～,、,和。Visual BasicVisual JVisual CVisual C++ 微软提供了“直通软”的软件的和,和～Visual Studio 2010Visual BasicVisual CVisual C + +和版本～不需任何软用。、年和软软版～以及Visual Web DeveloperVisual Studio 201020082005 的特定软言版本;、、,、,,～通软微软的下软Visual Studio 2005Visual BasicC++CJ 软～软生免软。划学DreamSpark 2架构 不支持任何软程软言～解方案或工具本软。相反～允软入各软功能。特定的功决它插Visual Studio 能是作软一个软软包的代软。安软～软功能可以服软器得到。装个从提供三软服软,～VSIDESVsSolution它决提供了能软列软的软目和解方案～提供了口和用软界面功能;包括软软～工具软和工它窗; SVsUIShell 具口,和窗～软理它软软包的注。此外～册软可以软软软软和服软之软软软通信。所有的软软器～SVsShellVSIDE
外文资料 Object landscapes and lifetimes Technically, OOP is just about abstract data typing, inheritance, and polymorphism, but other issues can be at least as important. The remainder of this section will cover these issues. One of the most important factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object controlled? There are different philosophies at work here. C++ takes the approach that control of efficiency is the most important issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocation and release, and control of these can be very valuable in some situations. However, you sacrifice flexibility because you must know the exact quantity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided design, warehouse management, or air-traffic control, this is too restrictive. The second approach is to create objects dynamically in a pool of memory called the heap. In this approach, you don't know until run-time how many objects you need, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is running. If you need a new object, you simply make it on the heap at the point that you need it. Because the storage is managed dynamically, at run-time, the amount of time required to allocate storage on the heap is significantly longer than the time to create storage on the stack. (Creating storage on the stack is often a single assembly instruction to move the stack pointer down, and another to move it back up.) The dynamic approach makes the generally logical assumption that objects tend to be complicated, so the extra overhead of finding storage and releasing that storage will not have an important impact on the creation of an object. In addition, the greater flexibility is essential to solve the general
A Rapid Tag Identification Method with Two Slots in RFID Systems Yong Hwan Kim, Sung Soo Kim, Kwang Seon Ahn Department of Computer Engineering, Kyungpook National University Daegu, Korea {hypnus, ninny, gsahn}@knu.ac.kr Abstract—RFID is core technology in the area of ubiquitous compu-ting. Identify the objects begin with the reader’s query to the tag at-tached to the subject. When multiple tags exist in the reader’s inter-rogation zone, these tags simultaneously respond to the reader’s query, resulting in collision. In RFID system, the reader needs the anti-collision algorithm which can quickly identify all the tags in the interrogation zone. This paper proposes tree based Rapid Tag Identi-fication Method with Two Slots(RTIMTS). The proposed algorithm rapidly identifies a tag with the information of Two Slots and MSB(Most Significant Bit). Two Slots resolve the tag collision by receiving the response from the tag to the Slot 0 and 1. The reader can identify two tags at once using MSB of information added to the tag ID. With RTIMTS algorithm, the total time of tag identification can be shortened by decreasing the number of query-responses from the reader. Keywords-RFID; Anti-collision; Two Slots; the number of query-responses. I.I NTRODUCTION RFID(Radio Frequency Identification) is a technology that deciphers or identifies the tag information through a reader (or interrogator) without contact. RFID have become very popular in many service industries, purchasing and distribution logis-tics, industry, manufacturing companies and material flow systems. Automatic Identification procedures exist to provide information about people, animals, goods and products in tran-sit[1][2]. The reader receives required information from the tags by sending and receiving wireless signals with the tag. Since the communication between the readers and the tags shares wire-less channels, there exist collisions. The collisions can be di-vided into the reader collision and the tag collision. The reader collision occurs when multiple readers send request signals to one tag, and the tag receives the wrong request signal due to signal interference between readers. The tag collision occurs when more than two tags simultaneously respond to one reader and the reader cannot identify any tags. This kind of collision makes the reader take long time to identify tags within the read-er’s identification range and impossible to identify even one tag[3][4][5] [6]. Therefore, the collision is a crucial problem that must be re-solved in RFID systems, so many studies to resolve this prob-lem have been carried out as well as are ongoing. This paper focuses on the tag collision problem which occurs in the case where one reader identifies multiple tags. Figure 1 provides schematizations of reader collision and tag collision. This paper proposes the Rapid Tag Identification Method with Two Slots (RTIMTS), for faster tag identification in mul-ti-tag environment where one reader identifies multiple tags. In the transfer paper[7], the proposed algorithm designs the method that it does without the value extracting procedure of even(or odd) parity bit of ID bit(T pb),the number of identified ‘1’s(T1n), the number of remaining ‘1’s(T rn), and the number of collided bit (T cb) with simple it can predict a tagID. Maximum 4 tag IDs can be identified on one round by using Two slots. a) The Reader collision b) The Tag collision Figure 1. The collision problem in RFID System II.T HE R ELATED WORKS A. Query Tree Query Tree(QT) algorithm is a binary tree based anti colli-sion algorithm and has an advantage in easily implementation due to its simple operating mode[8]. QT sets the reader’s query and tag’s response as one round, and identifies tags by iterating the round. In each round, the reader requests prefix to tag’s ID. And when ID matches the prefix, each tag transmits all IDs including prefixes to the reader. At this time, if more than one tag simultaneously responds, the reader cannot recognize tag’s ID, but can recognize that there are currently more than two tags having the prefix. Then the reader adds ‘0’ or ‘1’ to the current prefix and queries the longer prefix to the tags again. When only one tag responds to the reader, it identifies the tag. In other words, the reader adds the prefix by 1 bit until only one tag responds and iterates this process until identifying all the tags within the range. Figure 2 shows the operating process of QT algorithms[10]. Figure 2 shows the process that four tags respond according to the readers’ query. In round 1, 2, 3, and 7, the collision oc-curs because more than two tags respond, and in round 4, 5, 8, and 9, tag can be identified because only one tag responds. The digital coding method applied to QT cannot detect the collision bits. When a collision occurs, the reader adds ‘0’ or ‘1’ to the 2009 Eighth IEEE International Symposium on Network Computing and Applications 978-0-7695-3698-9/09 $25.00 ? 2009 IEEE DOI 10.1109/NCA.2009.21 292