In Proceedings of the First International World Wide Web Conference, Geneva, Switzerland, 1994. Early Web crawlers simply followed every link acquiring more and more pages. The focused crawler is different in using a topic taxonomy, learning from example, and using graph distillation to track topical hubs. However the customization is on searching of Web pages, not building a personal Web page database. Thus the purpose is different from ours.
Agents have energy, which is gained from relevant Web pages and lost from irrelevant pages.
Agents having hight energy can reproduce themselves and others having low energy may die. P. D. Bra and R. Post. In the First International WWW Conference, 1994. TueMosaic and the WebCrawler are two prominent early examples. In Proceedings of the First International World Wide Web Conference '94, Geneva, Switzerland, 1994.