Zillman estimates that thousands of bots are roaming the Internet. Many of the agent programs are free to try. Definitions of the technology are a bit muddy, varying from source to source. Simple bots rely on pre- programmed preferences to blindly fetch and filter information. More sophisticated agents make inferences from user feedback to determine how to satisfy a request.
Some agents are simple to use, others much more complex.
To get some agents started, you simply go to a Web site and fill out a form. To kick off other agents, you must download the agent software and install it on your machine. It helps shoppers check out hundreds of products peddled online including books, computers and cigars. N.Y.-based International Business Machines Corp. ''remembers'' where Web surfers have been on the Web and helps them recall visited pages. It also automatically checks favorite Web pages for changes.