Shedding Light on the Hidden Web

The terms Hidden Web, Deep Web and Invisible Web describe those resources on the Web that are in some way unreachable by search engines, and are potentially unusable to other Web systems such as annotation services. These hidden resources make up a signicant part of the current Web. We provide rm denitions of the ways in which information can be "hidden", and discuss the challenges that face those working with annotation in the Hidden Web. We do not attempt to provide solutions for these challenges, but a clarification of the terms involved is certainly a step in the right direction.