数据库系统中，数据库用户使用的数据视图用（ ）描述。

以下关于数据仓库的叙述中，不正确的是（ ）。

在通信专业中，PON的英文全称是“（ ）”，“衰减”英文通常翻译为“（ ） ”。

IPv6 was developed by the （ ） to deal with the long-anticipated problem of IPv4 adderss exhaustion．

There are a number of key technologies that will enable LTE Advanced to achieve the high data （ ） rates that are required．（ ） are two of the base technologies that will be enablers．Along with these there a number of other techniques and technologies that will be employed．

Software defined networking(SDN) is a telecommunications network （ ） that provides the promise of significant improvements in the network （ ）.