n. The collection of searchable websites whose content exists within databases and so cannot be indexed by search engines.
While the aforementioned Internet search resources are essential for 'on the Internet' searching, they do not and cannot find and make all that is 'on the Internet' accessible. They also do not make the material found in 'traditional library databases' searchable and accessible….This 'hidden' information is often called the 'Invisible Web.' To see what I mean have a look at my Direct Search compilation or the Lycos Invisible Web Collection.
To view the data that resides on what PLS calls the 'Invisible Web', users would have to subscribe to several private data services and perform multiple searches to find which database is best for their needs. With AT1, the user will know immediately where the data is, on or below the Visible or World Wide Web.