1、什么是middleware,有什么功能？
Middleware is computer software that connects software components or applications. It is used most often to support complex, distributed applications. It includes web servers, application servers, content management systems, and similar tools that support application development and delivery. Middleware is especially integral to modern information based on XML, SOAP, Web services, and service-oriented architecture.
中间件是连接应用软件或组件的一种软件，通常用来支持整合或分布式应用，包括WEB服务，应用服务器，CMS以及其他类似的东东。中间件在XML，SOAP，SOA的应用中特别需要。
2、objectweb的定义
Middleware is the enabling technology of Enterprise application integration. It describes a piece of software that allows two or more software applications to connect together so that they can exchange data.
ObjectWeb defines middleware as "the software layer that lies between the operating system and the applications on each side" of a distributed computing system.
中间件是一种能够整合企业应用的技术，它是一种可以让两个或更多应用软件连接在一起交换数据的软件。
objectweb定义中间件是分布式系统中一个介于操作系统和应用软件之间的层次。
3、起源
Middleware is a relatively new addition to the computing landscape. It gained popularity in the 1980's as a solution to the problem of how to link new applications to older legacy systems, although the term had been in use since 1968. It also facilitated distributed processing – the connection of multiple applications together to create a larger application, usually over a network.
中间为计算机发展的前景提供了新的选择，作为一种连接新老系统的解决方案，老系统中甚至有1968年起用的，所以它在上实际80年代赢得很好的声誉。它还推动了基于网络的分布式计算的发展，分布式计算是一种靠连接多个应用形成一个大的新应用的方式。
4、组织
In addition to the existing vendors updating their wares to address the newly expanded vision, vendors such as Mercator, Vitria, and webMethods were specifically founded to provide Web-oriented middleware tools. Groups such as the Apache Software Foundation and the ObjectWeb Consortium encourage the development of open source middleware.
除了已经存在的供应商升级了他们的产品以便应对延伸的应用之外，象mercator,vitria,webmethods都特别提供了面向WEB的中间件产品。象apache和objectweb这样的组织鼓励开源的中间件。
5、中间件的类型
Hurwitz's classification system that organizes the many types of middleware that are currently available. These classifications are based on scalability and recoverability:
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Remote Procedure Call (RPCs) - Client makes calls to procedures running on remote systems. Can be asynchronous or synchronous.
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Publish/subscribe - This type of middleware monitors activity and pushes relevant information to subscribers.
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Message Oriented Middleware (MOM) - Messages sent to the client are collected and stored until they are acted upon, while the client continues with other processing.
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Object Request Broker (ORB) - This type of middleware makes it possible for applications to send objects and request services in an object-oriented system.
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SQL-oriented Data Access - middleware between applications and database servers.
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Other sources include these additional classifications:
- Transaction processing (TP) monitors - Provides tools and an environment for developing and deploying distributed applications.
- Application servers - software installed on a computer to facilitate the serving (running) of other applications.
- Enterprise Service Bus - An abstraction layer on top of an Enterprise Messaging System.
1、RPCs 远程调用：客户端调用远程系统上的应用，呼叫和可以是同步或异步的。
2、MOM 面向消息的中间件：发送到客户端的消息被收集和存储起来直到他们被遵照执行，同时客户端还继续进行其他操作。
3、publish/subscribe 发布/订阅：这种类型的中间件监视和发布相关信息给订阅者。
4、ORB 对象请求代理：它可以在一个面向对象的系统中（OO system)建立对象之间的client/server关系。通过ORB，一个client可以透明的引用同一台机器上或网络上的一个server对象的方法。
5、SQL-oriented Data Access 应用程序和数据库服务之间的中间件
6其他的如下：
TP monitors 事物处理监视器：用于分布式系统
application servers 应用服务：安装在一台计算机上用来实现帮助其他应用服务
ESB 企业服务总线：抽取出来的东东，SOA中。。