企业应用集成的概览
Interesting applications rarely live in isolation. Whether your sales application must interface with your inventory application, your procurement application must connect to an auction site, or your PDA’s PIM must synchronize with the corporate calendar server, it seems like any application can be made better by integrating it with other applications.（好的应用很少孤立地存在，是否你的销售系统必须要和库存系统做接口，你的采购系统要连上外部商品出售系统，甚至你的手持设备，通俗说就是智能手机啦安卓爱疯之类的了，需要和你所在公司的日程办公系统同步啊，这里是我杜撰的：>,所有这些看来说明任何程序通过与其它程序集成沟通才能表现得更好啊）
All integration solutions have to deal with a few fundamental challenges:
* Networks are unreliable. Integration solutions have to transport data from one computer to another across networks. Compared to a process running on a single computer, distributed computing has to be prepared to deal with a much larger set of possible problems. Often times, two systems to be integrated are separated by continents and data between them has to travel through phone-lines, LAN segments, routers, switches, public networks, and satellite links. Each of these steps can cause delays or interruptions.
* Networks are slow. Sending data across a network is multiple orders of magnitude slower than making a local method call. Designing a widely distributed solution the same way you would approach a single application could have disastrous performance implications.
* Any two applications are different. Integration solutions need to transmit information between systems that use different programming languages, operating platforms, and data formats. An integration solution needs to be able to interface with all these different technologies.
* Change is inevitable. Applications change over time. An integration solution has to keep pace with changes in the applications it connects. Integration solutions can easily get caught in an avalanche effect of changes – if one system changes, all other systems may be affected. An integration solution needs to minimize the dependencies from one system to another by using loose coupling between applications.
（所有得集成方案都要面对以下这些基本挑战：
1.网络是不可靠的：集成方案必须要靠网络传输数据，和单机系统相比，分布式处理必须要处理更多可能的问题。经常情况下，两个需要集成的系统跨越两块大陆，译者注：<这个太极端了，除非是跨国企业，或者面向全球的用户的网站，我这里说得是可能都在中国，只是两个系统是由不同的组织维护，在不同的机房，你知道在中国南北通信之类，联通和移动不连通等问题的>，它们之间的数据传输通过慢速的电话线，通过局域网、路由器、交换机、公共网络等。这其中每一步都肯那个引起延迟或者中断。
2，网络有时很慢：译者：<本人所在公司做的这个集成项目就遇到过此类问题，在局域网调试跑得好好的单点登录系统，拿到公网上就不行了，这个问题的解决很是费了一番脑筋，就是个子系统之间处理通讯同步时的网络或者程序上的处理延迟问题，所以以后若是讲到单点登录系统会详细说明>具体不翻译了。
3.参与集成的各个架构及所采用技术，编程语言可能不同，这里不具体翻译了。
4.变化是必然的：用俗话说是唯一的不变就是变化。需求变化，规模变化，环境变化，还包括领导变化等，这一切的一切都可能需要调整程序，那么怎么一种不变或者说少变化应对外部的变化呢，那就是松耦合，减少强依赖，<笔者在这里自由发挥，可以具体看看意思大致相同>
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这章主要是讲概念，及为什么要采用异步消息系统等，以后具体再写，想快速的阅读以后的章节了。
