They work like this: The first time a site is visited, it installs a tracking file, which assigns the computer a unique ID number.

其工作原理如下：用户第一次访问某个站点时，就会安装一个追踪文件，该文件给计算机分配一个唯一性的ID号。

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If more than one data source procedure or function has the same name and number of parameters, then the UNIQUE ID needs to be specified.

如果多个数据源过程或函数具有同样的名称和参数数量，那么需要指定UNIQUE ID。

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Like a serial port, each USB port on a computer is assigned a unique identification number (port id) by the USB controller.

像串行端口一样，计算机上每一个usb端口都由US b控制器指定了一个惟一的标识数字(端口id)。

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Besides using a third party authenticator consistently at every game, Major League Baseball allows its fans to trace their memorabilia purchases online by using a unique ID number and hologram.

FORBES: Buyer Beware: The Fragility Of The Sports Memorabilia Industry

Another notable feature is the unique, hard-coded ID number Intel assigns to each chip.

CNN: Graphics applications scream on Intel Pentium III

The certificate itself contains the issuer's name (for example, Chase Manhattan), a serial number, a signature algorithm ID, an expiration date, an employee's public key and unique identifiers for both the issuer and the employee.

CNN: Technology - E-Signature Act may drive demand for authentication technology