The reason for this is simple: These actions require people to understand where they are in an interactive system and how to find and actuate what they want.

• 这就很不幸了，按道理讲，和各种各样的物理世界中的机械系统相比，数字世界应该有能力提供给我们更加优越的查找信息的手段，我们下面要谈的是如何提高这种检索能力。