Superimposed Information for the Internet

It has existed for several millennia, in the form of commentaries on religious books, law and literature. We see it today in concordances, citation indexes and genome maps. You probably have created some of it, as a bookmark file in your web browser. The “it” we refer to is superimposed information: data “placed over” existing information sources to help organize, access, connect and reuse information elements in those sources.