Web users, who have diverse interests and demands, can benefit from the endless options offered by various Web-based information sources and service providers. Moreover, their benefits increase if intermediaries personalize the content. Maglio and Barrett categorize intermediary services along two dimensions: where they run (for example, the user’s client, the information provider’s server, or an intermediary server), and the function they perform (for example, filter, annotate, aggregate, or cache).

Web Intermediaries (WBI) is a framework consisting of a programmable HTTP proxy server. It was designed to allow easy implementation of various intermediary applications, such as personal histories; shortcut links within sites the user visits regularly; or a dictionary intermediary that provides links to definitions.

The authors’ two-dimensional categorization of intermediary services is a valuable tool for analyzing existing intermediaries and systematically designing new ones. Although the authors supply links to intermediary services on the Internet, they provide references only to their own publications and fail to cite other works or Web resources.