End users perforce learned how to invoke applications via commands.

最终用户必须学会如何通过命令来调用应用程序。

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You can choreograph these services into composite applications and invoke them through standard protocols, as shown in Figure 2 below.

你可以将这些服务设计成合成的应用程序并且通过标准协议来调用它们，如下面的图2所示。

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What happens when you invoke callback functions defined by other applications?

当调用由其他应用程序定义的回调函数时会发生什么？

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