若某面向对象系统中的某子模块需要为其他模块提供访问不同数据库系统(Oracle、SQLServer、DB2 UDB等)的功能，这些数据库系统提供的访问接口有一定的差异，但访问过程却都是相同的，例如，先连接数据库，再打开数据库，最后对数据进行查询。(50)设计模式可抽象出相同的数据库访问过程。

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SOX is an alternative (71) for XML. It is useful for reading and creating XML content in a (72) editor. It is then easily transformed into proper XML. SOX was created because developers can spend a great deal of time with raw XML. For many of us, the popular XML (73) have not reached a point where their tree views, tables and forms can completely substitute for the underlying (74) language. This is not surprising when one considers that developers still use a text view, albeit enhanced, for editing other languages such as Java. SOX uses (75) to represent the structure of an XML document, which eliminates the need for closing tags and a number of quoting devices. The result is surprisingly clear.

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从数据库管理系统的角度看，数据库系统通常采用如图2-10所示的三级模式结构。图中①②处应填写(52)，③处应填写(53)。

某单位内部局域网中，客户机通过基于Windows操作系统的代理服务器访问Internet的连接方式如图 2-11所示。地址为192.168.1.100的客户机配置“TCP/IP网络属性”时，其中“网关”的设置内容应是(69)。该客户机访问Internet时，经由代理服务器后数据包的源地址为(70)。

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