Whats wrong with filtering based on keyword searches?
Keyword searching is a crude and inflexible approach that is likely to block sites that should not be blocked while letting “adult” sites pass through unblocked. These problems are tied to two shortcomings of this approach: Keyword searches cannot use contextual information. While searches can identify the presence of certain words in a text, they cannot evaluate the context in which those words are used. For example, a search might find the word “breast” on a web page, but it cannot determine whether that word was used in a chicken recipe, an erotic story, or in some other manner. In one notable incident, America Online’s keyword searches blocked a breast cancer support group. Keyword searches cannot interpret graphics. It is not currently possible to “search” the contents of a picture. Therefore, a page containing sexually explicit pictures will be blocked only if the text on that page contains one or more words from the list of words to be blocked.
